Multicentric Reticulohistiocytosis (MRH) - Mystery Diagnosis





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Published on Jan 19, 2014

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).

Signs and symptoms:

MRH is a rare, systemic histiocytic disease that mainly affects the skin and joints. Joint involvement primarily manifests with symmetric polyarthritis with a predilection for the distal interphalangeal joints. However, several other joints may be affected. The rates of distribution of joint disease are as follows: Hands (76%) Knees (73%) Shoulders (64%) Wrists (64%) Hips (61%) Ankles (58%) Elbows (58%) Feet (58%) Spine (52%)

Skin involvement generally manifests with translucent reddish-brown to flesh-colored papulonodules varying from 1-2 mm to 1 cm in diameter or larger. Lesions may be isolated from one another, or they may be clustered, sometimes giving them a cobblestone appearance.

The lesions are usually nontender, although some patients may complain of pruritus, which can be diffuse. The nodules grow slowly and rarely ulcerate. Infiltrated plaques may resemble mucinosis. Although MRH lesions have a predilection for the hands and face, they may occur on any surface of the body.

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