Erdheim-Chester disease: A rare multisystem histiocytic disorder associated with interstitial lung disease

Erdheim-Chester disease (ECD) is a rare multisystem histiocytosis syndrome of unknown cause that usually affects adults. Histiocytic infiltration of m ultiple end organs produces bone pain, xanthelasma and xanthoma, exophthalm os, diabetes insipidus, and interstitial lung disease. Differential diagnos is includes Langerhans cell histiocytosis, metabolic disorders, malignancy, and sarcoidosis. ECD can be diagnosed using a combination of clinical and histopathologic findings. Sites of involvement include lung, bone, skin, re troorbital tissue, central nervous system, pituitary gland, retroperitoneum , and pericardium. Symmetrical long bone pain with associated osteoscleroti c lesions, xanthomas around the eyelids, exophthalmos, and/or diabetes insi pidus suggest ECD. Approximately 35% of patients have associated lung invol vement, characterized by interstitial accumulations of histiocytic cells an d fibrosis in a predominantly perilymphangitic and subpleural pattern. This pattern distinguishes ECD from other histiocytic disorders involving the l ung. The diagnosis is confirmed by tissue biopsies that contain histiocytes with non-Langerhans cell features. In general, the clinical course of pati ents with this disease varies, and the prognosis can be poor despite treatm ent. Clinical trials for treatment of ECD have not been conducted and treat ment is based on anecdotal experience.