This Mystery Diagnosis episode is about Multicentric Reticulohistiocytosis. Multicentric reticulohistiocytosis (MRH) is a rare disease in which papulonodular skin lesions containing a proliferation of true histiocytes (macrophages) are associated with arthritis that primarily affects the interphalangeal joints. MRH is not life threatening and, after an average course of 7-8 years, the disease often goes into remission. However, in 45% of cases, the associated arthritis may cause severe joint destruction known as arthritis mutilans.
In addition to the joints, MRH can involve the bones, tendons, and muscles, as well as almost any organ (eg, the eyes, larynx, thyroid, salivary glands, bone marrow, heart, lungs, kidneys, liver, gastrointestinal tract).