A case of vemurafenib-induced keratosis pilaris-like eruption

Vemurafenib, a selective BRAF kinase inhibitor, is a new anti-cancer drug recently proven to improve survival in patients with metastatic melanoma harboring the BRAF V600E mutation. BRAF is one of three RAF kinases (ARAF, BRAF, CRAF) involved in the MAP kinase pathway. Mutations in BRAF are reported to be present in 40 to 70 percent of melanomas and in lower frequencies in various other malignancies. The BRAF V600E mutation is a specific valine to glutamic acid single substitution that constitutes 80 to 90 percent of reported BRAF mutations. Successful treatment of metastatic melanoma with vemurafenib is not without significant adverse effects. The most common toxic effects of this drug include rash, arthralgia, and fatigue. Less commonly, cases of follicular cystic lesions, keratoacanthoma, and squamous cell carcinoma have also been described. We report a case of a patient with metastatic melanoma treated with vemurafenib, who developed diffuse follicular hyperkeratosis resembling keratosis pilaris. To our knowledge, this is the first reported case of a keratosis pilaris-like side effect of vemurafenib.