Case of Erdheim-Chester presenting with xanthelasma-like eruption and osteolytic bone lesions: A case report.

Erdheim-Chester disease is a rare multisystemic non-Langerhans cell histiocytosis presenting 95% with skeletal lesions. Erdheim-Chester disease is due to mutations in the RAS-MEK-ERK pathway where 50% are due to BRAF-V600E mutations. Typical histopathological, clinical, and radiologic features are necessary for the diagnosis of Erdheim-Chester disease. Prognosis depends on the extent of the systemic involvement, and central nervous system involvement has a poorer outcome. We present a 30-year-old Moroccan woman with diabetes insipidus, bone marrow, and asymmetrical axial osteolytic bone lesions. Biopsies were consistent with Erdheim-Chester disease. Despite no treatment, the patient has demonstrated clinical improvement.