Lichenoid drug reaction to vemurafenib

Abstract

Approximately 40–60% of malignant melanomas (MM) demonstrate mutations of BRAF. 1 , 2 Clinical trials have shown improved survival in patients with metastatic MM treated with vemurafenib (R05185426/PLX4032), a BRAF inhibitor which particularly targets cases with the V600E mutation. 3 , 4 Common cutaneous adverse events reported in patients treated with vemurafenib include photosensitivity, rash, alopecia and squamoproliferative lesions. Photosensitive skin rash occurs in 12% of patients, 3 however the histological features of this reaction have not been described to date. We describe the histological features of two patients treated with vemurafenib for stage IV metastatic MM who developed a photosensitive eruption. Patient 1 was a 40-year-old male who developed a widespread, photosensitive, papular eruption within 4 weeks of commencing treatment. Patient 2 was a 58-year-old male who developed a similar cutaneous eruption also within 4 weeks of commencing treatment. Biopsies from both patients showed a lichenoid interface dermatitis, which was mild in case 1, with a similar though more florid reaction with focal acantholysis in case 2. Both cases demonstrated superficial and deep perivascular dermal inflammatory infiltrates composed predominantly of lymphocytes. The rash improved in both patients following reduction of the drug dose.