Late emergence of myasthenia gravis complicating envenoming by Viperaammodytes

Vipera ammodytes, is the most important medically venomous snake in North Macedonia and one of the most dangerous species in Europe.

A 41-year-old construction worker sustained a bite to the distal phalanx of his right thumb while lifting a brick. The injury was followed by local swelling and visual disturbances. Initial management at a regional medical center included administration of specific antivenom, tetanus prophylaxis, methylprednisolone, chloropyramine, prophylactic anticoagulation, and antibiotic therapy, resulting in transient clinical improvement. Over the following two weeks, the patient developed progressive neurological symptoms, including headache, dizziness, bilateral ptosis, diplopia, transient vision loss, worsening dysphagia, generalized muscle weakness, and fatigue. He was referred to a tertiary toxicology clinic, where an acute myasthenic syndrome was suspected. A diagnostic trial with subcutaneous neostigmine combined with atropine led to rapid improvement of ptosis, confirming a cholinesterase inhibition response. Treatment with pyridostigmine and prednisone was initiated. After discharge, the patient initially improved but discontinued therapy on his own after three weeks. Six months later, during follow-up, neurological symptoms worsened, including increased weakness in the right hand. Additionally, he developed deformity and limited mobility of the distal interphalangeal joint at the bite site. After neurological reassessment, treatment was resumed, and regular follow-up examinations were scheduled thereafter.

Although the acute management of snakebite envenomation primarily focuses on life-threatening complications, less severe venom-related effects may be overlooked during this stage. Therefore, long-term monitoring of the patient's clinical status is necessary, with periodic reassessment and adjustment of the therapeutic approach.