Eruptive Junctional Nevi Appearing During Langerhans Cell Histiocytosis Treatment

Langerhans cell histiocytosis (LCH) is a multisystemic disorder that results from the clonal proliferation of immunophenotypically and functionally immature Langerhans cells (LC). The detection of the V600E mutation in the BRAF oncogene in LCH biopsy specimens supports previous evidence that LCH is a neoplastic disorder. This mutation is present in other cutaneous lesions including malignant melanoma and benign nevi. Single case reports of a correlation between LCH and the appearance of eruptive nevi limited to the inguinal folds after chemotherapy have previously been described in the literature. This suggested that LCH could be an additional cause of eruptive melanocytic nevi, with a specific distribution mimicking that of LCH cutaneous lesions. We present the case of a 6-year-old boy, previously treated with chemotherapy for Langerhans cell histiocytosis, with disseminated junctional nevi. Although this co-occurrence may be coincidental, the skin involvement is distinct from other previously reported clinical cases. It would be interesting to evaluate whether the BRAF mutation described in LCH cells might in fact support a genetic background for the development of nevi in these patients. LEARNING POINTS: Langerhans cell histiocytosis (LCH) is a clonal neoplastic proliferation of immature Langerhans cells, with the V600E mutation in the BRAF oncogene present in approximately 60% of cases. The V600E mutation in the BRAF oncogene is also documented in other cutaneous lesions, namely malignant melanoma and benign nevi. There are case reports of a correlation between LCH and the appearance of eruptive nevi after chemotherapy, but it is not known whether the BRAF mutation described in LCH cells supports a genetic background for the development of nevi in these patients.