Dabrafenib-Induced Cutaneous Eruptions in a Patient With Langerhans Cell Histiocytosis.

Langerhans cell histiocytosis (LCH) is a rare malignancy marked by clonal proliferation of Langerhans cells, with BRAF V600E mutations identified in over 50% of the cases. BRAF inhibitors (BRAFi), such as dabrafenib, have shown efficacy in treating BRAF V600E-mutant LCH. However, BRAFi therapy is associated with cutaneous adverse effects, including the development of new melanocytic nevi, verrucae, and keratinocyte carcinoma (KC). This case report describes a 78-year-old woman with BRAF V600E-mutant LCH who developed multiple dermatologic side effects following dabrafenib salvage therapy. Seven weeks into treatment, the patient presented with eruptive palmoplantar nevi, verrucae, and a basal cell carcinoma (BCC). Biopsies revealed endophytic verruca vulgaris and acral junctional melanocytic nevus. A previous history of KC and photodamage likely contributed to the development of BCC. Additionally, the patient experienced arthralgias and Dupuytren's contracture, consistent with known BRAFi side effects. While the cutaneous manifestations observed here have been documented in BRAF V600E-mutant melanoma, this case is unique in its presentation in LCH patients. This report emphasizes the need for routine dermatologic monitoring and awareness of potential skin malignancies and other side effects in adults undergoing BRAFi therapy for LCH.