Eruptive Nevi in a BRAF Positive Child with Three Histiocytic Disorders

Summary: Our patient is a three-year-old male with a history of Rosai-Dorfman (RDD), juvenile xanthogranuloma (JXG), and Langerhans Cell Histiocytosis (LCH) who finished chemotherapy in 2018. He was treated with vincristine, vinblastine, decadron, and cytarabine for a high-risk orbital lesion. The patient presented for a follow-up of his histiocytic disorders. At this time, his mother indicated an increase in what she described as freckles or moles located on his abdomen. The patient and family were told to monitor the lesions. The physician suspected they could have arisen from the chemotherapy. Our patient returned to the clinic in 2022, where he was formally diagnosed with multiple eruptive nevi. He underwent genetic testing later that year and was confirmed to host the V600E BRAF mutation. Eruptive melanocytic nevi (EMN) represent a peculiar finding defined as the rapid onset of multiple melanocytic nevi. Eruptive nevi have associated with the onset with medications, immunosuppression, severe blistering diseases, and malignancy. Other reports demonstrate an association between EMN and LCH, especially in patients with the V600E BRAF mutation.1-3 We suggest this case provides further evidence that the BRAF mutation could be behind the pathogenesis of eruptive nevi. To the best of our knowledge, no other cases have reported eruptive nevi with RDD or JXG. Dermatologists should consider genetic testing when patients present with eruptive nevi, especially in the setting of a histiocytic disorder.