Langerhans cell histiocytosis in non‐twin siblings

Langerhans cell histiocytosis (LCH), which has unknown pathogenesis, can manifest as many kinds of signs and symptoms at any age. Although its genetic background has not been exactly identified, the familial clustering of this disease has been described in some reports. It is very uncommon, however, in siblings who are not monozygotic or dizygotic twins. Reported herein is a case of LCH in non‐twin siblings (younger sister and elder brother) who were diagnosed at 3.3 and 14.5 years of age, respectively, and successfully treated with chemotherapy, with BRAF V600E mutation status, and a brief review of the literature.