Mixed Langerhans Cell Histiocytosis and Erdheim-Chester Disease in a Girl: A Rare and Puzzling Diagnosis

OBJECTIVE: The objective of this study was to report the case of a girl diagnosed as suffering from multisystem, BRAF V600E-positive refractory Langerhans cell histiocytosis (LCH) and coexistent Erdheim-Chester disease (ECD) with perirenal, intracranial involvement and the dramatic response to clofarabine treatment. OBSERVATIONS: Histiocytoses are rare diseases with a broad clinical spectrum. Recent evidence supports a molecular and clinical overlap between LCH and ECD, and mixed LCH/ECD is now a separate entity. However, only a few pediatric cases of mixed disease have been reported in the literature. CONCLUSIONS: In a child with refractory, multisystem histiocytosis and atypical presentations, mixed LCH/ECD should be suspected in the differential diagnosis.