A Bite by a Beaded Lizard,Heloderma spp. (Helodermatidae),Resulting in Local Envenomation and Boutonnière Deformity

Abstract

Beaded lizards (Heloderma spp) are venomous lizards capable of inflicting local and systemic envenoming. An exotic pet collector presented with a reportedly prolonged bite by a presumed Guatemalan beaded lizard (Heloderma charlesbogerti). He reported immediate symptoms of envenoming, including severe pain, paresthesia, local swelling, dizziness, and nausea. Follow-up assessments conducted over a period of up to 4 y revealed a persistent boutonnière deformity of the right middle finger. This case report describes envenomation caused by the uncommonly documented bite of a beaded lizard (Heloderma spp) that was presumed by the patient to be the rare Guatemalan beaded lizard (H charlesbogerti). It illustrates the risks of long-term sequelae that may result from noncompliance with treatment after a helodermatid bite and also reemphasizes concerns about the underground sale of rare, endangered wildlife. Beaded lizard bites can inflict severe local envenomation and potentially cause permanent hand deformities. Proper referral and follow-up are essential to prevent long-term sequelae.

Introduction

A bite from a beaded lizard (Heloderma spp; family Helodermatidae) can cause severe local and systemic envenomation. Case reports of bites by any of the 4 recognized species of beaded lizards are scarce.^1,2 In this case report we describe a patient who was bitten by a presumed Guatemalan beaded lizard (Heloderma charlesbogerti) and subsequently developed local envenomation as well as a boutonnière deformity. H charlesbogerti was recently elevated to species status from the subspecies Heloderma horridum charlesbogerti. ³

Case Report

Our patient was a 43-y-old exotic pet collector with good past health. While changing the water bowl for his pet Guatemalan beaded lizard (presumably H charlesbogerti, according to the patient; see Figure 1), he was bitten on his right middle finger. The identity of the lizard was reported by the patient; a clear photograph of the specimen was reviewed, and the general identity was affirmed by a local toxicologist with a special interest in reptiles. The Guatemalan beaded lizard was a 2-y-old subadult with a snout-vent length of 300 mm. The patient then took the lizard out of the box and placed it on a desk, waiting for its disengagement to occur. He was aware that further struggling might result in a stronger bite, and he was reluctant to hurt the lizard. Its jaw remained attached to the patient's finger for ∼10 min before it was released spontaneously. During this time, the patient described a sensation of his finger being chewed. He also experienced severe pain and paresthesia in the right middle finger. After disengagement of the bite, immediate swelling of the finger developed. Over the next 30 min, the pain and paresthesia progressed to involve the patient’s forearm, upper arm, and axilla, accompanied by dizziness and nausea. The dizziness and nausea gradually subsided over 2 to 3 h. However, the pain and paresthesia persisted, and the swelling extended to the right dorsum of the hand. The patient attended the emergency department 4 h after the bite. His blood pressure was 148/85 mm Hg, and his heart rate was 110 beats/min. Physical examination revealed a bite mark over the medial side of the proximal phalanx of the right middle finger along with significant swelling involving the right middle finger and hand (Figure 2). Due to the swelling, movement of the proximal and distal interphalangeal joints of the right middle finger was limited. The patient rated his pain as 10 out of 10 on the numeric rating scale. Wound cleaning and dressing were performed, and tetanus prophylaxis was administered. The patient declined blood tests. Examination of the wound did not reveal any tooth fragments. There was no further progression of the swelling during the following 12-h observation period. The patient’s blood pressure measured at 6 h after the bite was 123/74 mm Hg, and on discharge was 128/82 mm Hg. The patient requested outpatient management and was discharged home with a course of oral acetaminophen, a nonsteroidal anti-inflammatory drug, and amoxicillin-clavulanate. A follow-up appointment arranged 2 d afterwards showed a reduction in swelling, and the patient indicated that the pain had decreased to 6 out of 10 on the rating scale. Follow-up at 2 wk showed residual mild swelling over the proximal interphalangeal joint. The patient reported that the pain had completely subsided on the fourth day after the bite. However, he complained of persistent difficulty in extending the proximal interphalangeal joint, whereas extension of the distal interphalangeal joint was normal. Physical examination revealed a boutonnière deformity of the right middle finger with scarring of the bite mark at the proximal interphalangeal joint (Figure 3). Tendon injury was suspected, and the patient was referred to the orthopedics team for assessment and an occupational therapist for splinting. The patient, however, defaulted on the orthopedic follow-up appointment and exhibited poor compliance with splinting. The patient also missed our follow-up appointment after 3 mo. At the 6-mo follow-up, the patient demonstrated persistence of the boutonnière deformity but claimed that it did not affect his activities of daily living and refused further referral. Clinical examination during consultation for an alleged ball python (Python regius) bite showed that the boutonnière deformity remained obvious 4 y afterwards (Figure 4).

Figure 1.

Patient's pet beaded lizard (photo provided by patient).

Figure 2.

Significant swelling involving the right middle finger and hand after the bite.

Figure 3.

Boutonnière deformity of the right middle finger with scarring of the bite mark at proximal interphalangeal joint at 2 wk after injury.

Figure 4.

Boutonnière deformity remained obvious 4 y later.

Discussion

In contrast to the 15-s bite reported in the literature for the first documented case of a Guatemalan beaded lizard bite, ¹ our patient experienced a significantly longer bite lasting 10 min, which may explain the more severe local toxicity observed. Similar to that first patient, ¹ our patient also experienced progression of pain and paresthesia beyond the bite site and developed systemic symptoms such as nausea and dizziness. Helodermatidae venom contains multiple toxins. Gilatoxin ⁴ and helothermine ⁵ may account for the paresthesia, ¹ whereas helodermatine, ⁶ horridum toxin, ⁷ and kallikrein-like toxic components ⁸ likely contribute to the severe pain. ¹ The genome of the Guatemalan beaded lizard contains genes with significant similarities to the associated proteins in the major helodermatid toxin classes. ⁹ Heloderma envenomation could potentially cause hypotension or hypertension, ¹⁰ with hypertension more common in Heloderma suspectum envenomation. In our patient, blood pressure on presentation was elevated, although his baseline blood pressure was unknown.

Heloderma venom glands are not associated with compressor musculature; instead, jaw movements create local capillary action that propels the venom into the grooves of the venom-conducting teeth. The venom thus is delivered by capillary action, and the jaw movements generated by the lizard may further propel the venom into the wound. The chewing sensation described by the patient during the 10-min bite likely corresponds to these repetitive jaw movements, which facilitate the delivery of the toxin. ⁸

Unfortunately, our patient developed long-term sequelae due to the bite. Tendon injuries, although often reported in mammalian bites, have been reported less frequently in lizard bites.^11,12 The patient's tendon injury may have resulted from the bite trauma caused by the prolonged chewing of the beaded lizard, leading to a more severe local injury. Extensor tendon injuries are more common than flexor tendon injuries in cases of small penetrating lacerations. ¹³ The patient's failure to adhere to the recommended treatment during the initial weeks following the bite also may have contributed to his long-term complications. Timely referral and further management by orthopedic specialists are crucial in reducing the risk of permanent deformity. ¹⁴

A major limitation of this case report is that the presumed identity of the lizard was reported by the patient and was not formally verified. Only 1 photo of the specimen was available, and without an informed herpetologist's assistance, the presumed species, H charlesbogerti, could not be confidently differentiated from H horridum or any of the other 3 beaded lizard species. It is important to note that H charlesbogerti is critically endangered ¹⁵ (https://link.springer.com/article/10.1007/s10592-022-01448-4), and if the identity is accurate, it is highly likely that the lizard was a smuggled, illegally obtained specimen.

Conclusions

Beaded lizard (Heloderma spp) bites can inflict severe local envenomation and potentially result in permanent hand deformities. Proper referral and follow-up are essential to reduce the risk of long-term sequelae.