A Case of Severe Thrombocytopenia and Antiepileptic Hypersensitivity Syndrome

Thrombocytopenia is a known complication of antiepileptic drug therapy. We present a case of a 3-year-old child who developed fever, rash, and severe thrombocytopenia within 10 days of initiating therapy with carbamazepine for new onset epilepsy. The patient's thrombocytopenia resolved following discontinuation of carbamazepine and introduction of valproic acid, however, his seizure disorder became poorly controlled. Phenobarbital was added to valproic acid therapy, which resulted in reoccurrence of fever, rash, and thrombocytopenia consistent with antiepileptic hypersensitivity syndrome. Discontinuation of phenobarbital, valproic acid and introduction of zonisamide resulted in resolution of his symptoms. The potential etiologies of thrombocytopenia in this case include carbamazepine-induced antiepileptic hypersensitivity syndrome, phenobarbital-induced antiepileptic hypersensitivity syndrome as a result of cross-reactivity with carbamazepine, and/or dose-dependent thrombocytopenia caused by valproic acid therapy. The pathogenesis and cases of aromatic anticonvulsant-induced immune-mediated thrombocytopenia are discussed. Alternative therapies for antiepileptic hypersensitivity syndrome with thrombocytopenia include gabapentin, levetiracetam, tiagabine, topiramate, and zonisamide.