Erdheim-Chester disease (ECD) is a rare subtype of non-Langerhans cell histiocytosis characterized by the accumulation of lipid-laden CD68, CD168, factor XIIIa positive, CD1a-negative macrophages, with Touton giant cells and surrounding fibrosis in multiple organs. More than half of cases are associated with a BRAF^V600E mutation. The disease can coexist with Langerhans histiocytosis (LCH).

The majority of patients are males between ages 40 and 60 at the time of diagnosis.

Patients typically present with multiorgan involvement including bone pain or fractures secondary to bilateral symmetric sclerosis of peripheral long bones, central diabetes insipidus, and other neurological symptoms, such as gait abnormalities. Cardiac, pulmonary, retroperitoneal, and cutaneous involvement occur less frequently.

Less than a third of patients present with cutaneous manifestations. Xanthelasma-like papules and plaques are most frequently seen. Other reported cutaneous manifestations include erythematous widespread patches or plaques on face, trunk, or extremities; discrete brownish plaques on the trunk; yellow-red nodules on the trunk; and brown hyperkeratotic plaques on the legs. Panniculitis-like nodules on the legs and annular plaques resembling granuloma annulare have also been described.

Some patients have indolent disease without symptoms. Others experience symptoms from a single organ system. Prognosis tends to be poor for patients with central nervous system involvement.