Suspected phenobarbitone induced pemphigus vulgaris in a dog

Abstract A 9‐year‐old male, neutered French bulldog, was presented with cluster seizures. Low field magnetic resonance imaging (MRI) of the head identified a left piriform lobe mass suspected neoplastic, likely glioma, and less likely post‐ictal change. Good seizure control was achieved with levetiracetam and phenobarbitone. Two weeks later, the dog developed ptyalism and ulceration of multiple mucous membranes. A biopsy was performed with histopathology consistent with pemphigus vulgaris. Due to clinical suspicion of a phenobarbitone idiosyncratic reaction, phenobarbitone was rapidly weaned, and the dog was treated with anti‐inflammatory corticosteroids and antibiotics. Eleven days later, repeat MRI confirmed a persistent mass lesion, and oral ulcerative lesions had resolved. This supported a presumptive glioma, hence the dog underwent stereotactic radiation and ongoing levetiracetam therapy. The dog remained seizure free with an incomplete reduction of the mass on repeat MRI 4 months following. This case describes a suspected drug‐induced pemphigus vulgaris and a potentially rare adverse effect of phenobarbitone.