Does the BRAF(V600E) mutation herald a new treatment era for Erdheim-Chester disease? A case-based review of a rare and difficult to diagnose disorder.

Erdheim-Chester disease is a multi-system histiocyte disorder characterised by histological xanthogranulomatous inflammation. We report a 67-year-old man who had fatal multi-systemic Erdheim-Chester disease involvement, including retroperitoneal fibrosis, dilated cardiomyopathy and bone pain that was diagnosed late in its course and was refractory to interferon-alfa. A pathogenic BRAF(V600E) mutation, identified after death in this patient, provides insights into pathogenesis and opens potential lines of treatment.