Overlap syndrome of Erdheim-Chester disease and Langerhans cell histiocytosis: A case report.

Langerhans cell histiocytosis (LCH) and Erdheim-Chester disease (ECD) are exceptionally rare disorders characterized by varied clinical presentations, posing several challenges for clinicians. The concomitant occurrence of LCH and ECD is exceedingly rare and has no known etiology. In this report, we present a rare case of mixed histiocytosis (both ECD and LCH) with multisystem involvement. The patient, a 49-year-old female, initially presented with a rash 2 years ago and progressively developed exophthalmos, fatigue, and shortness of breath. She lacked the mutation in codon 600 of exon 15 of B-Raf proto-oncogene (BRAF-V600E) and subsequently underwent treatment with corticosteroids, interferon-alpha, and chemotherapy, all of which proved ineffective. This work highlights the urgent need to improve treatment outcomes for such patients. Therefore, we discuss the latest advancements in understanding treatment strategies for mixed histiocytic syndromes.