Xanthogranulomatous reaction to trametinib for metastatic malignant melanoma.

Trametinib, a mitogen-activated extracellular signal-regulated kinase (MEK) inhibitor, has demonstrated great promise in treating metastatic melanoma associated with BRAF V600E and V600K mutations; however, it also is highly associated with cutaneous adverse events (AEs). As both BRAF and MEK inhibitors become increasingly used to treat malignant melanoma, it is important to better characterize these AEs so that we can manage them. Herein, we present a case of a 66-year-old man who developed erythematous scaly papules on the face and bilateral upper extremities after beginning therapy with trametinib. The severity of the reaction worsened on trametinib monotherapy compared to combination therapy with a BRAF inhibitor. Biopsy revealed a xanthogranulomatous reaction.