Erdheim-Chester Disease With BRAF V600E Mutation and Central Diabetes Insipidus Successfully Treated With Glucocorticoid.

Erdheim-Chester disease (ECD) is a rare non-Langerhans cell histiocytosis characterized by xanthoma/xanthogranuloma infiltration in various organs and a broad spectrum of clinical presentations, including bone lesions, central diabetes insipidus and renal failure. BRAF V600E mutation is seen in almost half of the cases of ECD; the BRAF inhibitor vemurafenib is recommended treatment in the United States and the European Union. However, the indication for vemurafenib in Japan is limited to unresectable malignant melanoma with BRAF mutation. Although glucocorticoids, interferon, chemotherapy, and radiation therapy are treatment options, no standard therapy for ECD has yet been established in Japan. We describe here a patient with central diabetes insipidus and retroperitoneal lesions who was successfully treated with prednisolone. Glucocorticoid therapy is therefore a plausible alternative for ECD with BRAF V600E mutation when the BRAF inhibitor vemurafenib cannot be used.