Dirk Elston, MD

North American venomous snakes traditionally are classified as members of either the Viperidae (eg, rattlesnakes, copperheads, cottonmouths) or Elapidae (eg, coral snakes) families and account for roughly 5000 to 10,000 reported envenomations annually.^1,2 In 2021, America’s Poison Centers reported 2287 calls related to copperheads, 71 related to coral snakes, 229 related to cottonmouths, 1184 related to rattlesnakes, and 524 related to unknown snakes.³ The majority of calls related to snake bites were for adult patients, resulting in absent to minor outcomes. Only 1 death due to a rattlesnake bite was reported.³ Death by envenomation from a North American snake species is considered rare and typically is attributed to a lapse in medical attention; however, rattlesnakes are the most common reported cause of death by snake envenomation (Figure 1).^1,3 A study comparing snake bites and hospital stays in the southeast vs southwest United States found that the southeast had the highest incidence of copperhead bites (37%), while the southwest had a higher incidence of rattlesnake bites (70%); those who were bitten by a rattlesnake were reported to have more severe symptoms and greater need for medical attention and antivenin.⁴ Some reports have linked pediatric and elderly patients to worse outcomes.⁵ However, one study examining 24,388 emergency department visits for snake bites from 2006 through 2014 found that the majority of pediatric cases were handled by non– trauma centers in the southern United States,⁶ supporting evidence found by Campbell et al⁷ indicating that most snake bites in children can be managed with conservative care. Though reported complications—including weakness, paralysis, hypovolemic shock, thrombocytopenia, and death—from North American venomous snake bites are low, they are still considered a medical emergency.⁸ It is essential for physicians to understand the clinical manifestations and treatment of North American venomous snake bites and to educate patients on how to protect themselves against and avoid provoking snakes, particularly in rural areas.² In this article, we review the characteristics of common North American venomous snakes and the clinical manifestations of their bites. We also discuss the appropriate measures for staging, evaluating, and treating snake envenomation to improve patient management and care.

Features of North American Venomous Snakes

Individual snakes within the Viperidae family vary in size, markings and coloration, activity, and region, and physicians should consult their local health departments regarding snakes that are common in their area.² Cottonmouth snakes are semiaquatic and traditionally are found within the southern and central United States. With a spade-shaped head and distinct two-tone coloration, cottonmouths may be mistaken for other nonvenomous water snakes in these regions (Figure 2).² Copperheads, true to their name, are red in color; they inhabit a large portion of the southeastern United States and eastern Texas regions and are the cause of the majority of venomous snake bites in North America (Figure 3). Both cottonmouths and copperheads are believed to bite and envenomate as a defensive mechanism when provoked.

Coral snakes, found in the eastern United States and Texas regions, are the only subspecies of the Elapidae family (Figure 4).^2,9 They can be distinguished from the nonvenomous milk snake by their characteristic banding, as coral snakes are patterned in a red-yellow-black band sequence and milk snakes are patterned in a red-black-yellow or white sequence. The differences in appearance of these snakes often is remembered by the phrase “red on yellow kills a fellow.”

Anatomic differences between the Viperidae and Elapidae families, including fang size, placement, and type, as well as venom composition, are directly linked to clinical manifestations of the bites. Viperidae fangs extend from the maxillary bones and are mobile, long, and hollow, making it easy for the snake to control fang movement and envenomation.⁹ Viperidae snakes are uniquely capable of inflicting puncture wounds without the injection of venom, known as dry bites. In contrast, Elapidae snakes have short, hollow, and fixed fangs, and thus patients can protect themselves by wearing appropriate clothing and covered footwear.⁹ Currently, identifying the type of snake responsible for the bite relies on visualization of the snake and/or the identification of clinical symptoms of envenomation by a dermatologist.

Clinical Manifestations of Venomous Snake Bites

Clinical manifestations and cutaneous findings often are used to grade the severity of venomous snake bites as well as to dictate treatment procedures. Grade 0 indicates a bite has occurred without envenomation, while grades I to V describe the progression and severity of envenomation.¹⁰ Grade I describes minimal erythema and edema around the site (fang marks may or may not be present) and no systemic symptoms. Grade II describes erythema and edema extending up the extremity to the first joint (eg, hand to wrist), pain, some systemic symptoms if there is rapid progression, and potential bleeding at the site. Grade III describes erythema and edema spreading to the second joint in the extremity, pain, and systemic symptoms, including coagulation defects. Grade IV describes erythema and edema of the whole extremity, a rapid reaction and progression following the bite, and risk for compartment syndrome. Grade V includes erythema and edema beyond the extremity and increasing systemic symptoms.¹⁰

Local pain and edema, usually on easily accessible or exposed extremities, are the most common clinical symptoms reported following a Viperidae snake bite.¹¹ Due to their capability of producing a dry bite, puncture markings alone do not indicate envenomation. Patients will need to be monitored for several hours for signs of envenomation, which may include swelling, pain, ecchymosis, and indications of systemic manifestation (eg, weakness, dizziness, nausea, severe hypotension, thrombocytopenia).¹¹ Viperidae venom hemorrhagic metalloproteinases act on capillary blood vessels by cleaving basement membrane proteins and allowing for extravasation of fluid into local tissue.¹² The inflammatory response produced at the site of envenomation likely is due to the release of tumor necrosis factor á and endogenous matrix metalloprotein.¹² There is a higher risk for death associated with bites from rattlesnakes within the Viperidae family because their venom contains a unique neurotoxin that works by blocking presynaptic junctions and causing a range of paralytic symptoms from ptosis to respiratory failure.¹³

The severity of Elapidae bites is thought to be related to the amount of venom injected, the size of the victim, and the length of the snake. Though clothing may offer protection, envenomation occurs in 75% of coral snake bites and can produce devastating consequences due to the venom content.¹⁴ In a retrospective study between 2002 and 2004, 90% of Elapidae snake bite patients (n=82) reported local pain, redness, and paresthesia, while around 7% developed systemic symptoms.¹⁵ Elapidae venom primarily is neurotoxic and is thought to spread via lymphatics.¹⁶ Delayed reactions are common and may take up to 12 hours to develop. Patients should be monitored, as local reactions may progress to weakness, fasciculations, extremity paralysis, and lastly, respiratory paralysis. Due to the risk for progression, all patients with likely coral snake bites should be given antivenin.^8,15,17

Much like the North American coral snake, the venomous snake species Gloydius blomhoffii—referred to as the salmosa or mamushi snake depending on the region of origin (ie, Korea or Japan)—is a frequent source of devastating rural snake bites due to neurotoxins (Figure 5). The species’ slender fangs are thought to directly inject the snake’s potent venom, which contains hemorrhagic toxins and α-neurotoxins and Β-neurotoxins, into the bloodstream; however, the salmosa is considered a viper like the North American cottonmouth and copperhead because of its triangular head shape and hollow fangs, which allow for the accommodation of venom-containing glands and mechanism of venom injection. Salmosa venom shares both Viperidae and Elapidae characteristics. Cutaneous findings such as progressive edema, erythema, and bleeding frequently are reported and are attributed to the proteases and hemorrhagic toxins characteristic of vipers (Figure 6). α-Neurotoxins and Β-neurotoxins, similar to the proteolytic venom of the Elapidae family, are responsible for the unique visual disturbances (binocular diplopia) caused by the salmosa.^12,18,19

Treatment

Treating snake bites begins with assessing the patient’s airway, breathing, and circulation, followed by a thorough medical and encounter history (including description of how the bite occurred). Due to the range of Viperidae symptoms, it generally is recommended that patients remove any restrictive clothing or jewelry near the bite and/or over the affected limb or body part, place the affected body part at the level of the heart, and go to the nearest medical facility for prompt care. Historically, empiric antibiotics often were used to prevent wound infections; however, studies have since demonstrated that antibiotics are not necessary and lack efficacy in uncomplicated snake bites.^16,20 In a study of 114 pediatric cases from 1995 to 2005, it was determined that most patients could be managed with conservative treatment directed at pain management and swelling reduction via elevation of the affected extremity.⁶ While conservative management may be all that is needed to care for the majority of cases, one retrospective study from Texas indicated that 70% of pediatric venomous snake bites were treated with either intravenous antibiotics and/or antivenin, highlighting the variability in management and opportunity for improvement.²¹

Antivenin, specifically antivenin (Crotalidae) polyvalent, is the indicated treatment for Viperidae hemorrhagic or coagulopathic envenomation.^13,22 Per guidelines from the World Health Organization, physical examination will yield a grading of the snake bite based on cutaneous findings. Grades III to V are considered moderate to severe and should be given antivenin.²³ Physicians should look for signs of progressive injury and coagulopathy, such as increased swelling, bruising, hypotension, or altered mental status.²² Due to the major neurotoxic risks associated with Elapidae venom, all coral snake bites should be treated with antivenin; early intubation and ventilation may be considered.¹³ Similarly, patients who report a salmosa snake bite require prompt treatment with antivenin and/or cepharanthine, an additive agent to reduce swelling and pain.¹⁸ Due to the nature of the neurotoxins contained in the salmosa venom (α-neurotoxin causing postsynaptic inhibition of the neuromuscular junction and Β-neurotoxin inhibiting neurotransmitter release from the presynaptic terminal), anticholinesterases, which work by blocking the enzymatic breakdown of the neurotransmitter acetylcholine, should not be used.¹⁹ While bleeding and skin and systemic changes may be reversed by antivenin, visual changes are unlikely to resolve with antivenin administration due to the presynaptic binding of Β-neurotoxin and the blockade of neuromuscular signaling.¹⁹

Antivenin should be administered intravenously for the fastest onset of action in a setting suitable for the management of anaphylaxis.²⁴ In situations when the benefits may outweigh the risks (eg, if the patient has had a prior allergic reaction or is not in an environment where they can be watched for at least 8 hours for progression of envenomation or adverse reactions), premedication with an antihistamine or epinephrine may be considered.17 Per the World Allergy Organization and World Health Organization, adverse reactions should be treated with crystalloid solutions and antihistamines, corticosteroids, or epinephrine as indicated.²⁵ In a qualitative analysis of emergency physicians’ attitudes toward antivenin, most expressed treatment hesitancy due to lack of knowledge and experience using the medication.²⁶ When possible, snake bites should thus be managed in consultation with a toxicologist.²

Conclusion

Snake bites and envenomation occur commonly in the United States due to exposure to a variety of venomous snakes in the North American Viperidae and Elapidae families. Appropriate and successful management of snake bites by physicians requires general knowledge of regional snakes, the cutaneous and systemic manifestations of snake bites and envenomation, and current treatment methods.

North American venomous snakes traditionally are classified as members of either the Viperidae (eg, rattlesnakes, copperheads, cottonmouths) or Elapidae (eg, coral snakes) families and account for roughly 5000 to 10,000 reported envenomations annually.^1,2 In 2021, America’s Poison Centers reported 2287 calls related to copperheads, 71 related to coral snakes, 229 related to cottonmouths, 1184 related to rattlesnakes, and 524 related to unknown snakes.³ The majority of calls related to snake bites were for adult patients, resulting in absent to minor outcomes. Only 1 death due to a rattlesnake bite was reported.³ Death by envenomation from a North American snake species is considered rare and typically is attributed to a lapse in medical attention; however, rattlesnakes are the most common reported cause of death by snake envenomation (Figure 1).^1,3 A study comparing snake bites and hospital stays in the southeast vs southwest United States found that the southeast had the highest incidence of copperhead bites (37%), while the southwest had a higher incidence of rattlesnake bites (70%); those who were bitten by a rattlesnake were reported to have more severe symptoms and greater need for medical attention and antivenin.⁴ Some reports have linked pediatric and elderly patients to worse outcomes.⁵ However, one study examining 24,388 emergency department visits for snake bites from 2006 through 2014 found that the majority of pediatric cases were handled by non– trauma centers in the southern United States,⁶ supporting evidence found by Campbell et al⁷ indicating that most snake bites in children can be managed with conservative care. Though reported complications—including weakness, paralysis, hypovolemic shock, thrombocytopenia, and death—from North American venomous snake bites are low, they are still considered a medical emergency.⁸ It is essential for physicians to understand the clinical manifestations and treatment of North American venomous snake bites and to educate patients on how to protect themselves against and avoid provoking snakes, particularly in rural areas.² In this article, we review the characteristics of common North American venomous snakes and the clinical manifestations of their bites. We also discuss the appropriate measures for staging, evaluating, and treating snake envenomation to improve patient management and care.

Features of North American Venomous Snakes

Individual snakes within the Viperidae family vary in size, markings and coloration, activity, and region, and physicians should consult their local health departments regarding snakes that are common in their area.² Cottonmouth snakes are semiaquatic and traditionally are found within the southern and central United States. With a spade-shaped head and distinct two-tone coloration, cottonmouths may be mistaken for other nonvenomous water snakes in these regions (Figure 2).² Copperheads, true to their name, are red in color; they inhabit a large portion of the southeastern United States and eastern Texas regions and are the cause of the majority of venomous snake bites in North America (Figure 3). Both cottonmouths and copperheads are believed to bite and envenomate as a defensive mechanism when provoked.

Coral snakes, found in the eastern United States and Texas regions, are the only subspecies of the Elapidae family (Figure 4).^2,9 They can be distinguished from the nonvenomous milk snake by their characteristic banding, as coral snakes are patterned in a red-yellow-black band sequence and milk snakes are patterned in a red-black-yellow or white sequence. The differences in appearance of these snakes often is remembered by the phrase “red on yellow kills a fellow.”

Anatomic differences between the Viperidae and Elapidae families, including fang size, placement, and type, as well as venom composition, are directly linked to clinical manifestations of the bites. Viperidae fangs extend from the maxillary bones and are mobile, long, and hollow, making it easy for the snake to control fang movement and envenomation.⁹ Viperidae snakes are uniquely capable of inflicting puncture wounds without the injection of venom, known as dry bites. In contrast, Elapidae snakes have short, hollow, and fixed fangs, and thus patients can protect themselves by wearing appropriate clothing and covered footwear.⁹ Currently, identifying the type of snake responsible for the bite relies on visualization of the snake and/or the identification of clinical symptoms of envenomation by a dermatologist.

Clinical Manifestations of Venomous Snake Bites

Clinical manifestations and cutaneous findings often are used to grade the severity of venomous snake bites as well as to dictate treatment procedures. Grade 0 indicates a bite has occurred without envenomation, while grades I to V describe the progression and severity of envenomation.¹⁰ Grade I describes minimal erythema and edema around the site (fang marks may or may not be present) and no systemic symptoms. Grade II describes erythema and edema extending up the extremity to the first joint (eg, hand to wrist), pain, some systemic symptoms if there is rapid progression, and potential bleeding at the site. Grade III describes erythema and edema spreading to the second joint in the extremity, pain, and systemic symptoms, including coagulation defects. Grade IV describes erythema and edema of the whole extremity, a rapid reaction and progression following the bite, and risk for compartment syndrome. Grade V includes erythema and edema beyond the extremity and increasing systemic symptoms.¹⁰

Local pain and edema, usually on easily accessible or exposed extremities, are the most common clinical symptoms reported following a Viperidae snake bite.¹¹ Due to their capability of producing a dry bite, puncture markings alone do not indicate envenomation. Patients will need to be monitored for several hours for signs of envenomation, which may include swelling, pain, ecchymosis, and indications of systemic manifestation (eg, weakness, dizziness, nausea, severe hypotension, thrombocytopenia).¹¹ Viperidae venom hemorrhagic metalloproteinases act on capillary blood vessels by cleaving basement membrane proteins and allowing for extravasation of fluid into local tissue.¹² The inflammatory response produced at the site of envenomation likely is due to the release of tumor necrosis factor á and endogenous matrix metalloprotein.¹² There is a higher risk for death associated with bites from rattlesnakes within the Viperidae family because their venom contains a unique neurotoxin that works by blocking presynaptic junctions and causing a range of paralytic symptoms from ptosis to respiratory failure.¹³

The severity of Elapidae bites is thought to be related to the amount of venom injected, the size of the victim, and the length of the snake. Though clothing may offer protection, envenomation occurs in 75% of coral snake bites and can produce devastating consequences due to the venom content.¹⁴ In a retrospective study between 2002 and 2004, 90% of Elapidae snake bite patients (n=82) reported local pain, redness, and paresthesia, while around 7% developed systemic symptoms.¹⁵ Elapidae venom primarily is neurotoxic and is thought to spread via lymphatics.¹⁶ Delayed reactions are common and may take up to 12 hours to develop. Patients should be monitored, as local reactions may progress to weakness, fasciculations, extremity paralysis, and lastly, respiratory paralysis. Due to the risk for progression, all patients with likely coral snake bites should be given antivenin.^8,15,17

Much like the North American coral snake, the venomous snake species Gloydius blomhoffii—referred to as the salmosa or mamushi snake depending on the region of origin (ie, Korea or Japan)—is a frequent source of devastating rural snake bites due to neurotoxins (Figure 5). The species’ slender fangs are thought to directly inject the snake’s potent venom, which contains hemorrhagic toxins and α-neurotoxins and Β-neurotoxins, into the bloodstream; however, the salmosa is considered a viper like the North American cottonmouth and copperhead because of its triangular head shape and hollow fangs, which allow for the accommodation of venom-containing glands and mechanism of venom injection. Salmosa venom shares both Viperidae and Elapidae characteristics. Cutaneous findings such as progressive edema, erythema, and bleeding frequently are reported and are attributed to the proteases and hemorrhagic toxins characteristic of vipers (Figure 6). α-Neurotoxins and Β-neurotoxins, similar to the proteolytic venom of the Elapidae family, are responsible for the unique visual disturbances (binocular diplopia) caused by the salmosa.^12,18,19

Treatment

Treating snake bites begins with assessing the patient’s airway, breathing, and circulation, followed by a thorough medical and encounter history (including description of how the bite occurred). Due to the range of Viperidae symptoms, it generally is recommended that patients remove any restrictive clothing or jewelry near the bite and/or over the affected limb or body part, place the affected body part at the level of the heart, and go to the nearest medical facility for prompt care. Historically, empiric antibiotics often were used to prevent wound infections; however, studies have since demonstrated that antibiotics are not necessary and lack efficacy in uncomplicated snake bites.^16,20 In a study of 114 pediatric cases from 1995 to 2005, it was determined that most patients could be managed with conservative treatment directed at pain management and swelling reduction via elevation of the affected extremity.⁶ While conservative management may be all that is needed to care for the majority of cases, one retrospective study from Texas indicated that 70% of pediatric venomous snake bites were treated with either intravenous antibiotics and/or antivenin, highlighting the variability in management and opportunity for improvement.²¹

Antivenin, specifically antivenin (Crotalidae) polyvalent, is the indicated treatment for Viperidae hemorrhagic or coagulopathic envenomation.^13,22 Per guidelines from the World Health Organization, physical examination will yield a grading of the snake bite based on cutaneous findings. Grades III to V are considered moderate to severe and should be given antivenin.²³ Physicians should look for signs of progressive injury and coagulopathy, such as increased swelling, bruising, hypotension, or altered mental status.²² Due to the major neurotoxic risks associated with Elapidae venom, all coral snake bites should be treated with antivenin; early intubation and ventilation may be considered.¹³ Similarly, patients who report a salmosa snake bite require prompt treatment with antivenin and/or cepharanthine, an additive agent to reduce swelling and pain.¹⁸ Due to the nature of the neurotoxins contained in the salmosa venom (α-neurotoxin causing postsynaptic inhibition of the neuromuscular junction and Β-neurotoxin inhibiting neurotransmitter release from the presynaptic terminal), anticholinesterases, which work by blocking the enzymatic breakdown of the neurotransmitter acetylcholine, should not be used.¹⁹ While bleeding and skin and systemic changes may be reversed by antivenin, visual changes are unlikely to resolve with antivenin administration due to the presynaptic binding of Β-neurotoxin and the blockade of neuromuscular signaling.¹⁹

Antivenin should be administered intravenously for the fastest onset of action in a setting suitable for the management of anaphylaxis.²⁴ In situations when the benefits may outweigh the risks (eg, if the patient has had a prior allergic reaction or is not in an environment where they can be watched for at least 8 hours for progression of envenomation or adverse reactions), premedication with an antihistamine or epinephrine may be considered.17 Per the World Allergy Organization and World Health Organization, adverse reactions should be treated with crystalloid solutions and antihistamines, corticosteroids, or epinephrine as indicated.²⁵ In a qualitative analysis of emergency physicians’ attitudes toward antivenin, most expressed treatment hesitancy due to lack of knowledge and experience using the medication.²⁶ When possible, snake bites should thus be managed in consultation with a toxicologist.²

Conclusion

Snake bites and envenomation occur commonly in the United States due to exposure to a variety of venomous snakes in the North American Viperidae and Elapidae families. Appropriate and successful management of snake bites by physicians requires general knowledge of regional snakes, the cutaneous and systemic manifestations of snake bites and envenomation, and current treatment methods.

North American venomous snakes traditionally are classified as members of either the Viperidae (eg, rattlesnakes, copperheads, cottonmouths) or Elapidae (eg, coral snakes) families and account for roughly 5000 to 10,000 reported envenomations annually.^1,2 In 2021, America’s Poison Centers reported 2287 calls related to copperheads, 71 related to coral snakes, 229 related to cottonmouths, 1184 related to rattlesnakes, and 524 related to unknown snakes.³ The majority of calls related to snake bites were for adult patients, resulting in absent to minor outcomes. Only 1 death due to a rattlesnake bite was reported.³ Death by envenomation from a North American snake species is considered rare and typically is attributed to a lapse in medical attention; however, rattlesnakes are the most common reported cause of death by snake envenomation (Figure 1).^1,3 A study comparing snake bites and hospital stays in the southeast vs southwest United States found that the southeast had the highest incidence of copperhead bites (37%), while the southwest had a higher incidence of rattlesnake bites (70%); those who were bitten by a rattlesnake were reported to have more severe symptoms and greater need for medical attention and antivenin.⁴ Some reports have linked pediatric and elderly patients to worse outcomes.⁵ However, one study examining 24,388 emergency department visits for snake bites from 2006 through 2014 found that the majority of pediatric cases were handled by non– trauma centers in the southern United States,⁶ supporting evidence found by Campbell et al⁷ indicating that most snake bites in children can be managed with conservative care. Though reported complications—including weakness, paralysis, hypovolemic shock, thrombocytopenia, and death—from North American venomous snake bites are low, they are still considered a medical emergency.⁸ It is essential for physicians to understand the clinical manifestations and treatment of North American venomous snake bites and to educate patients on how to protect themselves against and avoid provoking snakes, particularly in rural areas.² In this article, we review the characteristics of common North American venomous snakes and the clinical manifestations of their bites. We also discuss the appropriate measures for staging, evaluating, and treating snake envenomation to improve patient management and care.

Features of North American Venomous Snakes

Individual snakes within the Viperidae family vary in size, markings and coloration, activity, and region, and physicians should consult their local health departments regarding snakes that are common in their area.² Cottonmouth snakes are semiaquatic and traditionally are found within the southern and central United States. With a spade-shaped head and distinct two-tone coloration, cottonmouths may be mistaken for other nonvenomous water snakes in these regions (Figure 2).² Copperheads, true to their name, are red in color; they inhabit a large portion of the southeastern United States and eastern Texas regions and are the cause of the majority of venomous snake bites in North America (Figure 3). Both cottonmouths and copperheads are believed to bite and envenomate as a defensive mechanism when provoked.

Coral snakes, found in the eastern United States and Texas regions, are the only subspecies of the Elapidae family (Figure 4).^2,9 They can be distinguished from the nonvenomous milk snake by their characteristic banding, as coral snakes are patterned in a red-yellow-black band sequence and milk snakes are patterned in a red-black-yellow or white sequence. The differences in appearance of these snakes often is remembered by the phrase “red on yellow kills a fellow.”

Anatomic differences between the Viperidae and Elapidae families, including fang size, placement, and type, as well as venom composition, are directly linked to clinical manifestations of the bites. Viperidae fangs extend from the maxillary bones and are mobile, long, and hollow, making it easy for the snake to control fang movement and envenomation.⁹ Viperidae snakes are uniquely capable of inflicting puncture wounds without the injection of venom, known as dry bites. In contrast, Elapidae snakes have short, hollow, and fixed fangs, and thus patients can protect themselves by wearing appropriate clothing and covered footwear.⁹ Currently, identifying the type of snake responsible for the bite relies on visualization of the snake and/or the identification of clinical symptoms of envenomation by a dermatologist.

Clinical Manifestations of Venomous Snake Bites

Clinical manifestations and cutaneous findings often are used to grade the severity of venomous snake bites as well as to dictate treatment procedures. Grade 0 indicates a bite has occurred without envenomation, while grades I to V describe the progression and severity of envenomation.¹⁰ Grade I describes minimal erythema and edema around the site (fang marks may or may not be present) and no systemic symptoms. Grade II describes erythema and edema extending up the extremity to the first joint (eg, hand to wrist), pain, some systemic symptoms if there is rapid progression, and potential bleeding at the site. Grade III describes erythema and edema spreading to the second joint in the extremity, pain, and systemic symptoms, including coagulation defects. Grade IV describes erythema and edema of the whole extremity, a rapid reaction and progression following the bite, and risk for compartment syndrome. Grade V includes erythema and edema beyond the extremity and increasing systemic symptoms.¹⁰

Local pain and edema, usually on easily accessible or exposed extremities, are the most common clinical symptoms reported following a Viperidae snake bite.¹¹ Due to their capability of producing a dry bite, puncture markings alone do not indicate envenomation. Patients will need to be monitored for several hours for signs of envenomation, which may include swelling, pain, ecchymosis, and indications of systemic manifestation (eg, weakness, dizziness, nausea, severe hypotension, thrombocytopenia).¹¹ Viperidae venom hemorrhagic metalloproteinases act on capillary blood vessels by cleaving basement membrane proteins and allowing for extravasation of fluid into local tissue.¹² The inflammatory response produced at the site of envenomation likely is due to the release of tumor necrosis factor á and endogenous matrix metalloprotein.¹² There is a higher risk for death associated with bites from rattlesnakes within the Viperidae family because their venom contains a unique neurotoxin that works by blocking presynaptic junctions and causing a range of paralytic symptoms from ptosis to respiratory failure.¹³

The severity of Elapidae bites is thought to be related to the amount of venom injected, the size of the victim, and the length of the snake. Though clothing may offer protection, envenomation occurs in 75% of coral snake bites and can produce devastating consequences due to the venom content.¹⁴ In a retrospective study between 2002 and 2004, 90% of Elapidae snake bite patients (n=82) reported local pain, redness, and paresthesia, while around 7% developed systemic symptoms.¹⁵ Elapidae venom primarily is neurotoxic and is thought to spread via lymphatics.¹⁶ Delayed reactions are common and may take up to 12 hours to develop. Patients should be monitored, as local reactions may progress to weakness, fasciculations, extremity paralysis, and lastly, respiratory paralysis. Due to the risk for progression, all patients with likely coral snake bites should be given antivenin.^8,15,17

Much like the North American coral snake, the venomous snake species Gloydius blomhoffii—referred to as the salmosa or mamushi snake depending on the region of origin (ie, Korea or Japan)—is a frequent source of devastating rural snake bites due to neurotoxins (Figure 5). The species’ slender fangs are thought to directly inject the snake’s potent venom, which contains hemorrhagic toxins and α-neurotoxins and Β-neurotoxins, into the bloodstream; however, the salmosa is considered a viper like the North American cottonmouth and copperhead because of its triangular head shape and hollow fangs, which allow for the accommodation of venom-containing glands and mechanism of venom injection. Salmosa venom shares both Viperidae and Elapidae characteristics. Cutaneous findings such as progressive edema, erythema, and bleeding frequently are reported and are attributed to the proteases and hemorrhagic toxins characteristic of vipers (Figure 6). α-Neurotoxins and Β-neurotoxins, similar to the proteolytic venom of the Elapidae family, are responsible for the unique visual disturbances (binocular diplopia) caused by the salmosa.^12,18,19

Treatment

Treating snake bites begins with assessing the patient’s airway, breathing, and circulation, followed by a thorough medical and encounter history (including description of how the bite occurred). Due to the range of Viperidae symptoms, it generally is recommended that patients remove any restrictive clothing or jewelry near the bite and/or over the affected limb or body part, place the affected body part at the level of the heart, and go to the nearest medical facility for prompt care. Historically, empiric antibiotics often were used to prevent wound infections; however, studies have since demonstrated that antibiotics are not necessary and lack efficacy in uncomplicated snake bites.^16,20 In a study of 114 pediatric cases from 1995 to 2005, it was determined that most patients could be managed with conservative treatment directed at pain management and swelling reduction via elevation of the affected extremity.⁶ While conservative management may be all that is needed to care for the majority of cases, one retrospective study from Texas indicated that 70% of pediatric venomous snake bites were treated with either intravenous antibiotics and/or antivenin, highlighting the variability in management and opportunity for improvement.²¹

Antivenin, specifically antivenin (Crotalidae) polyvalent, is the indicated treatment for Viperidae hemorrhagic or coagulopathic envenomation.^13,22 Per guidelines from the World Health Organization, physical examination will yield a grading of the snake bite based on cutaneous findings. Grades III to V are considered moderate to severe and should be given antivenin.²³ Physicians should look for signs of progressive injury and coagulopathy, such as increased swelling, bruising, hypotension, or altered mental status.²² Due to the major neurotoxic risks associated with Elapidae venom, all coral snake bites should be treated with antivenin; early intubation and ventilation may be considered.¹³ Similarly, patients who report a salmosa snake bite require prompt treatment with antivenin and/or cepharanthine, an additive agent to reduce swelling and pain.¹⁸ Due to the nature of the neurotoxins contained in the salmosa venom (α-neurotoxin causing postsynaptic inhibition of the neuromuscular junction and Β-neurotoxin inhibiting neurotransmitter release from the presynaptic terminal), anticholinesterases, which work by blocking the enzymatic breakdown of the neurotransmitter acetylcholine, should not be used.¹⁹ While bleeding and skin and systemic changes may be reversed by antivenin, visual changes are unlikely to resolve with antivenin administration due to the presynaptic binding of Β-neurotoxin and the blockade of neuromuscular signaling.¹⁹

Antivenin should be administered intravenously for the fastest onset of action in a setting suitable for the management of anaphylaxis.²⁴ In situations when the benefits may outweigh the risks (eg, if the patient has had a prior allergic reaction or is not in an environment where they can be watched for at least 8 hours for progression of envenomation or adverse reactions), premedication with an antihistamine or epinephrine may be considered.17 Per the World Allergy Organization and World Health Organization, adverse reactions should be treated with crystalloid solutions and antihistamines, corticosteroids, or epinephrine as indicated.²⁵ In a qualitative analysis of emergency physicians’ attitudes toward antivenin, most expressed treatment hesitancy due to lack of knowledge and experience using the medication.²⁶ When possible, snake bites should thus be managed in consultation with a toxicologist.²

Conclusion

Snake bites and envenomation occur commonly in the United States due to exposure to a variety of venomous snakes in the North American Viperidae and Elapidae families. Appropriate and successful management of snake bites by physicians requires general knowledge of regional snakes, the cutaneous and systemic manifestations of snake bites and envenomation, and current treatment methods.

THE DIAGNOSIS: Hypertrophic Lupus Erythematosus

The biopsy of the face collected at the initial appointment revealed interface dermatitis with epidermal hyperplasia with no parakeratosis or eosinophils (Figure 1). Microscopic findings were suggestive of hypertrophic lupus erythematosus (HLE) or hypertrophic lichen planus. The rapid plasma reagin and HIV labs collected at the initial appointment were negative, and a review of systems was negative for systemic symptoms. Considering these results and the clinical distribution of the lesions primarily affecting sun-exposed areas of the upper body, a final diagnosis of HLE was made. The patient was counseled on the importance of photoprotection and was started on hydroxychloroquine.

Hypertrophic lupus erythematosus, a rare variant of chronic cutaneous lupus erythematosus (CCLE), typically manifests as verrucous plaques or nodules commonly found on sun-exposed areas of the body, as was observed in our patient on the face, scalp (Figures 2 and 3), chest, and upper extremities.¹ Lesions can have a variable appearance, from hyperkeratotic ulcers to depigmented plaques and keratoacanthomalike lesions.² On histopathology, HLE falls into the category of lichenoid interface dermatitis and commonly demonstrates hyperkeratosis, acanthosis, follicular plugging, superficial and deep infiltrate, and increased mucin deposition in the dermis.³

Although rare, it is critical to remain vigilant for the development of squamous cell carcinoma in patients with chronic untreated CCLE. Hypertrophic lupus erythematosus, specifically, is the most likely variant to give rise to invasive squamous cell carcinoma and can be more aggressive as a result of this malignant transformation.^3,4 Ruling out squamous cell carcinoma in the setting of HLE can be achieved by staining for CD123, as HLE commonly is associated with many CD123+ plasmacytoid dendritic cells adjacent to the epithelium, unlike squamous cell carcinoma.³ Fortunately no evidence of invasive squamous cell carcinoma, including cellular atypia or increased mitotic figures, was seen on histology in our patient.

A thorough history and physical examination are essential for screening for HLE, as positive antinuclear antibodies are observed only in half of the patients diagnosed with CCLE.⁵ Furthermore, antinuclear antibodies sometimes can be negative in patients with HLE who have end-stage organ involvement.

Hypertrophic lupus erythematosus can be challenging to treat. First-line therapies include antimalarials, topical steroids, and sun-protective measures. Intralesional triamcinolone injection also can be used as an adjunctive therapy to expedite the treatment response.⁶ Evidence supports good response following treatment with acitretin or a combination of isotretinoin and hydroxychloroquine.² Another therapeutic strategy is implementing immunosuppressants such as methotrexate, mycophenolate mofetil, and azathioprine for persistent disease. Immunomodulators such as thalidomide historically have been shown to treat severe recalcitrant cases of HLE but typically are reserved for extreme cases due to adverse effects. Biologic agents such as intravenous immunoglobulins and rituximab have been shown to treat CCLE successfully, but routine use is limited due to high cost and lack of strong clinical trials.⁷

There have been reports of experimental therapies such as monoclonal antibodies (eg, anifrolumab and tocilizumab therapy) providing remission for patients with refractory CCLE, but information on their efficacy—specifically in patients with HLE—is lacking.⁸ Chronic cutaneous lupus erythematosus and its variants require further investigation regarding which treatment options provide the greatest benefit while minimizing adverse effects.

It is important to distinguish HLE from other potential diagnoses. Features of HLE can mimic hypertrophic lichen planus; however, the latter typically appears on the legs while HLE appears more commonly on the upper extremities and face in a photodistributed pattern.⁹ Since HLE has a lichenoid appearance histologically, it may appear clinically similar to hypertrophic lichen planus. Although not performed in our patient due to cost, direct immunofluorescence can aid in distinguishing HLE from hypertrophic lichen planus. Chronic cutaneous lupus erythematosus shows a granular pattern of deposition of IgM (primarily), IgG, IgA, and C3. In contrast, hypertrophic lichen planus exhibits cytoid bodies that stain positive for IgM as well as linear deposition of fibrinogen along the basement membrane.^3,10

Blastomycosis also can lead to development of verrucous plaques in sun-exposed areas, but the lesions typically originate as pustules that ulcerate over time. Lesions also can manifest with central scarring and a heaped edge.³ Unlike HLE, pseudoepitheliomatous hyperplasia with mixed infiltrate and intradermal pustules are seen in blastomycosis.³ Fungal organisms often are seen on pathology and are relatively large and uniform in size and shape, are found within giant cells, and have a thick refractile asymmetrical wall.¹¹ In rupioid psoriasis, skin lesions mostly are widespread and are not limited to sun-exposed areas. Additionally, biopsies from active rupioid lesions typically show psoriasiform epidermal hyperplasia with parakeratosis with no interface inflammation—a key differentiator.¹² In secondary syphilis, chancres often are missed and are not reported by patients. Clinically, secondary syphilis often manifests as scaly patches and plaques with palmar involvement and positive rapid plasma reagin, which was negative in our patient.¹³ Histologically, secondary syphilis can exhibit a vacuolar or lichenoid interface dermatitis; however, it typically exhibits slender acanthosis with long rete ridges and neutrophils in the stratum corneum.³ Furthermore, plasma cells are present in about two-thirds of cases in the United States, with obliteration of the lumen of small vessels and perivascular histiocytes and lymphocytes with apparent cytoplasm commonly seen on pathology. Silver staining or immunostaining for Treponema pallidum may reveal the spirochetes that cause this condition.³

THE DIAGNOSIS: Hypertrophic Lupus Erythematosus

The biopsy of the face collected at the initial appointment revealed interface dermatitis with epidermal hyperplasia with no parakeratosis or eosinophils (Figure 1). Microscopic findings were suggestive of hypertrophic lupus erythematosus (HLE) or hypertrophic lichen planus. The rapid plasma reagin and HIV labs collected at the initial appointment were negative, and a review of systems was negative for systemic symptoms. Considering these results and the clinical distribution of the lesions primarily affecting sun-exposed areas of the upper body, a final diagnosis of HLE was made. The patient was counseled on the importance of photoprotection and was started on hydroxychloroquine.

Hypertrophic lupus erythematosus, a rare variant of chronic cutaneous lupus erythematosus (CCLE), typically manifests as verrucous plaques or nodules commonly found on sun-exposed areas of the body, as was observed in our patient on the face, scalp (Figures 2 and 3), chest, and upper extremities.¹ Lesions can have a variable appearance, from hyperkeratotic ulcers to depigmented plaques and keratoacanthomalike lesions.² On histopathology, HLE falls into the category of lichenoid interface dermatitis and commonly demonstrates hyperkeratosis, acanthosis, follicular plugging, superficial and deep infiltrate, and increased mucin deposition in the dermis.³

Although rare, it is critical to remain vigilant for the development of squamous cell carcinoma in patients with chronic untreated CCLE. Hypertrophic lupus erythematosus, specifically, is the most likely variant to give rise to invasive squamous cell carcinoma and can be more aggressive as a result of this malignant transformation.^3,4 Ruling out squamous cell carcinoma in the setting of HLE can be achieved by staining for CD123, as HLE commonly is associated with many CD123+ plasmacytoid dendritic cells adjacent to the epithelium, unlike squamous cell carcinoma.³ Fortunately no evidence of invasive squamous cell carcinoma, including cellular atypia or increased mitotic figures, was seen on histology in our patient.

A thorough history and physical examination are essential for screening for HLE, as positive antinuclear antibodies are observed only in half of the patients diagnosed with CCLE.⁵ Furthermore, antinuclear antibodies sometimes can be negative in patients with HLE who have end-stage organ involvement.

Hypertrophic lupus erythematosus can be challenging to treat. First-line therapies include antimalarials, topical steroids, and sun-protective measures. Intralesional triamcinolone injection also can be used as an adjunctive therapy to expedite the treatment response.⁶ Evidence supports good response following treatment with acitretin or a combination of isotretinoin and hydroxychloroquine.² Another therapeutic strategy is implementing immunosuppressants such as methotrexate, mycophenolate mofetil, and azathioprine for persistent disease. Immunomodulators such as thalidomide historically have been shown to treat severe recalcitrant cases of HLE but typically are reserved for extreme cases due to adverse effects. Biologic agents such as intravenous immunoglobulins and rituximab have been shown to treat CCLE successfully, but routine use is limited due to high cost and lack of strong clinical trials.⁷

There have been reports of experimental therapies such as monoclonal antibodies (eg, anifrolumab and tocilizumab therapy) providing remission for patients with refractory CCLE, but information on their efficacy—specifically in patients with HLE—is lacking.⁸ Chronic cutaneous lupus erythematosus and its variants require further investigation regarding which treatment options provide the greatest benefit while minimizing adverse effects.

It is important to distinguish HLE from other potential diagnoses. Features of HLE can mimic hypertrophic lichen planus; however, the latter typically appears on the legs while HLE appears more commonly on the upper extremities and face in a photodistributed pattern.⁹ Since HLE has a lichenoid appearance histologically, it may appear clinically similar to hypertrophic lichen planus. Although not performed in our patient due to cost, direct immunofluorescence can aid in distinguishing HLE from hypertrophic lichen planus. Chronic cutaneous lupus erythematosus shows a granular pattern of deposition of IgM (primarily), IgG, IgA, and C3. In contrast, hypertrophic lichen planus exhibits cytoid bodies that stain positive for IgM as well as linear deposition of fibrinogen along the basement membrane.^3,10

Blastomycosis also can lead to development of verrucous plaques in sun-exposed areas, but the lesions typically originate as pustules that ulcerate over time. Lesions also can manifest with central scarring and a heaped edge.³ Unlike HLE, pseudoepitheliomatous hyperplasia with mixed infiltrate and intradermal pustules are seen in blastomycosis.³ Fungal organisms often are seen on pathology and are relatively large and uniform in size and shape, are found within giant cells, and have a thick refractile asymmetrical wall.¹¹ In rupioid psoriasis, skin lesions mostly are widespread and are not limited to sun-exposed areas. Additionally, biopsies from active rupioid lesions typically show psoriasiform epidermal hyperplasia with parakeratosis with no interface inflammation—a key differentiator.¹² In secondary syphilis, chancres often are missed and are not reported by patients. Clinically, secondary syphilis often manifests as scaly patches and plaques with palmar involvement and positive rapid plasma reagin, which was negative in our patient.¹³ Histologically, secondary syphilis can exhibit a vacuolar or lichenoid interface dermatitis; however, it typically exhibits slender acanthosis with long rete ridges and neutrophils in the stratum corneum.³ Furthermore, plasma cells are present in about two-thirds of cases in the United States, with obliteration of the lumen of small vessels and perivascular histiocytes and lymphocytes with apparent cytoplasm commonly seen on pathology. Silver staining or immunostaining for Treponema pallidum may reveal the spirochetes that cause this condition.³

THE DIAGNOSIS: Hypertrophic Lupus Erythematosus

The biopsy of the face collected at the initial appointment revealed interface dermatitis with epidermal hyperplasia with no parakeratosis or eosinophils (Figure 1). Microscopic findings were suggestive of hypertrophic lupus erythematosus (HLE) or hypertrophic lichen planus. The rapid plasma reagin and HIV labs collected at the initial appointment were negative, and a review of systems was negative for systemic symptoms. Considering these results and the clinical distribution of the lesions primarily affecting sun-exposed areas of the upper body, a final diagnosis of HLE was made. The patient was counseled on the importance of photoprotection and was started on hydroxychloroquine.

Hypertrophic lupus erythematosus, a rare variant of chronic cutaneous lupus erythematosus (CCLE), typically manifests as verrucous plaques or nodules commonly found on sun-exposed areas of the body, as was observed in our patient on the face, scalp (Figures 2 and 3), chest, and upper extremities.¹ Lesions can have a variable appearance, from hyperkeratotic ulcers to depigmented plaques and keratoacanthomalike lesions.² On histopathology, HLE falls into the category of lichenoid interface dermatitis and commonly demonstrates hyperkeratosis, acanthosis, follicular plugging, superficial and deep infiltrate, and increased mucin deposition in the dermis.³

Although rare, it is critical to remain vigilant for the development of squamous cell carcinoma in patients with chronic untreated CCLE. Hypertrophic lupus erythematosus, specifically, is the most likely variant to give rise to invasive squamous cell carcinoma and can be more aggressive as a result of this malignant transformation.^3,4 Ruling out squamous cell carcinoma in the setting of HLE can be achieved by staining for CD123, as HLE commonly is associated with many CD123+ plasmacytoid dendritic cells adjacent to the epithelium, unlike squamous cell carcinoma.³ Fortunately no evidence of invasive squamous cell carcinoma, including cellular atypia or increased mitotic figures, was seen on histology in our patient.

A thorough history and physical examination are essential for screening for HLE, as positive antinuclear antibodies are observed only in half of the patients diagnosed with CCLE.⁵ Furthermore, antinuclear antibodies sometimes can be negative in patients with HLE who have end-stage organ involvement.

Hypertrophic lupus erythematosus can be challenging to treat. First-line therapies include antimalarials, topical steroids, and sun-protective measures. Intralesional triamcinolone injection also can be used as an adjunctive therapy to expedite the treatment response.⁶ Evidence supports good response following treatment with acitretin or a combination of isotretinoin and hydroxychloroquine.² Another therapeutic strategy is implementing immunosuppressants such as methotrexate, mycophenolate mofetil, and azathioprine for persistent disease. Immunomodulators such as thalidomide historically have been shown to treat severe recalcitrant cases of HLE but typically are reserved for extreme cases due to adverse effects. Biologic agents such as intravenous immunoglobulins and rituximab have been shown to treat CCLE successfully, but routine use is limited due to high cost and lack of strong clinical trials.⁷

There have been reports of experimental therapies such as monoclonal antibodies (eg, anifrolumab and tocilizumab therapy) providing remission for patients with refractory CCLE, but information on their efficacy—specifically in patients with HLE—is lacking.⁸ Chronic cutaneous lupus erythematosus and its variants require further investigation regarding which treatment options provide the greatest benefit while minimizing adverse effects.

It is important to distinguish HLE from other potential diagnoses. Features of HLE can mimic hypertrophic lichen planus; however, the latter typically appears on the legs while HLE appears more commonly on the upper extremities and face in a photodistributed pattern.⁹ Since HLE has a lichenoid appearance histologically, it may appear clinically similar to hypertrophic lichen planus. Although not performed in our patient due to cost, direct immunofluorescence can aid in distinguishing HLE from hypertrophic lichen planus. Chronic cutaneous lupus erythematosus shows a granular pattern of deposition of IgM (primarily), IgG, IgA, and C3. In contrast, hypertrophic lichen planus exhibits cytoid bodies that stain positive for IgM as well as linear deposition of fibrinogen along the basement membrane.^3,10

Blastomycosis also can lead to development of verrucous plaques in sun-exposed areas, but the lesions typically originate as pustules that ulcerate over time. Lesions also can manifest with central scarring and a heaped edge.³ Unlike HLE, pseudoepitheliomatous hyperplasia with mixed infiltrate and intradermal pustules are seen in blastomycosis.³ Fungal organisms often are seen on pathology and are relatively large and uniform in size and shape, are found within giant cells, and have a thick refractile asymmetrical wall.¹¹ In rupioid psoriasis, skin lesions mostly are widespread and are not limited to sun-exposed areas. Additionally, biopsies from active rupioid lesions typically show psoriasiform epidermal hyperplasia with parakeratosis with no interface inflammation—a key differentiator.¹² In secondary syphilis, chancres often are missed and are not reported by patients. Clinically, secondary syphilis often manifests as scaly patches and plaques with palmar involvement and positive rapid plasma reagin, which was negative in our patient.¹³ Histologically, secondary syphilis can exhibit a vacuolar or lichenoid interface dermatitis; however, it typically exhibits slender acanthosis with long rete ridges and neutrophils in the stratum corneum.³ Furthermore, plasma cells are present in about two-thirds of cases in the United States, with obliteration of the lumen of small vessels and perivascular histiocytes and lymphocytes with apparent cytoplasm commonly seen on pathology. Silver staining or immunostaining for Treponema pallidum may reveal the spirochetes that cause this condition.³