Vemurafenib-associated neutrophilic panniculitis: An emergent adverse effect of variable severity.

Vemurafenib is a selective BRAF kinase inhibitor recently proven to improve rates of overall and progression-free survival in patients with BRAF-V600-mutant metastatic melanoma. The most common adverse effects of this targeted therapy are arthralgia, fatigue, and cutaneous lesions, including alopecia, photosensitivity, pruritus, hand-foot skin reactions, squamous cell carcinomas, keratoacanthomas, warty dyskeratomas and verrucous keratosis. Less frequently, cases of panniculitis of varying severity have been reported in patients receiving vemurafenib. In this report, we describe a patient who developed asymptomatic nodules on her legs, with complete, spontaneous resolution, while on vemurafenib therapy. A causal relationship was considered likely because of the timing of occurrence and the absence of other potential causes after extensive assessment. Vemurafenib therapy was continued at full dosage and no recurrences were observed. We believe that management of lobular panniculitis associated with selective BRAF inhibitors should vary according to the clinical presentation, degree of systemic involvement, and presence of joint inflammation. Physicians should be aware of this emergent side effect. Treatment discontinuation should be considered on a case-by-case basis because the condition may resolve spontaneously.