Multicentric reticulohistiocytosis - Skin
The cutaneous eruption of MRH is characterized by gradually appearing papulonodules that most frequently occur on the acral areas of the body, especially the head, hands, and juxta-articular regions of the extremities. Approximately 33% of patients will experience pruritus of variable severity, and systemic symptoms such as fever, malaise, weakness, and weight loss often accompany the eruption. Leonine facies, xanthelasma, and nail dystrophy can also develop. In addition, some patients can be affected by a dermatomyositis-like photodistributed eruption. Mucous membrane involvement occurs in up to 50% of patients. The typical mucosal eruption is characterized by multiple erythematous papules and nodules affecting the oral and nasopharyngeal mucosa. Mucocutaneous disease typically lasts 5-10 years with subsequent regression.
Joint disease is a prominent feature of MRH that can produce significant morbidity. The typical presentation is a symmetric erosive polyarthritis that evolves into arthritis mutilans in up to 50% of patients. Progressive destruction of joints occurs in most individuals for about 6-8 years with stabilization thereafter. The distal interphalangeal (DIP) joints are affected most commonly (about 75% of cases), although any joint can be involved, including (in order of decreasing frequency): proximal interphalangeal (PIP), metacarpophalangeal (MCP), wrists, shoulders, knees, hips, ankles, feet, elbows, and spine.
Systemic involvement in MRH is not uncommon. In addition to skin, mucous membranes, and joints, other organ systems that can be affected include nerves, heart, lungs, eyes, gastrointestinal tract, salivary glands, and thyroid gland. Anemia (50%), elevated erythrocyte sedimentation rate (ESR), and dyslipidemia (30%-58%) are commonly observed laboratory abnormalities in patients with MRH. Rarely, patients are also noted to have IgG hypergammaglobulinemia and cryoglobulinemia. There are numerous reported associations with MRH, including malignancy (up to 25%), tuberculosis (12%-50%), autoimmune disorders, and systemic vasculitis. Carcinomas of the lung, breast, stomach, cervix, ovary, and colon are the most frequently associated malignancies, although lymphoma, leukemia, sarcoma, malignant mesothelioma, and malignant melanoma have also been reported, albeit less commonly.
Solitary cutaneous reticulohistiocytosis (or reticulohistiocytoma cutis) and diffuse cutaneous reticulohistiocytosis are two rare, distinct diagnostic concepts that occur without joint or other systemic involvement. The former presents as a solitary rapidly growing nodule, and the latter presents with mucocutaneous findings similar to classic MRH. A familial variant of MRH, called familial histiocytic dermatoarthritis, has also been reported in which classic mucocutaneous findings occur with typical ophthalmologic involvement (glaucoma, cataracts, uveitis).
D76.3 – Other histiocytosis syndromes
84241008 – Multicentric reticulohistiocytosis
- Rheumatoid arthritis – much more common, DIP joints are not involved, RF and anti-CCP antibody levels are positive, juxta-articular osteopenia is present on X-rays of affected joints, and histopathology reveals palisaded granulomas in the deep reticular dermis.
- Psoriatic arthritis – asymmetric involvement, classic skin and nail changes of psoriasis usually present, and X-rays demonstrate marginal erosions with periosteal new bone formation.
- Reactive arthritis (Reiter syndrome) – usually asymmetric involvement following genitourinary or gastrointestinal tract infection, frequently associated with conjunctivitis, urethritis, enthesitis, and/or mucocutaneous eruption (keratoderma blenorrhagicum and circinate balanitis), and X-rays demonstrate marginal erosions with periosteal new bone formation.
- Gout – usually asymmetric involvement, gouty tophi can be present, X-rays demonstrate nonmarginal erosions with overhanging edges, histopathology reveals granulomatous inflammation surrounding urate crystals, and joint aspirate will be positive for urate crystals; hyperuricemia and hyperuricosuria can be present.
- Erosive osteoarthritis – Heberden's and Bouchard's nodes are frequently present, and X-rays demonstrate central erosions, joint space narrowing, subchondral sclerosis, and osteophytes.
- Leprosy – characteristic involvement of skin (hypopigmented macules, annular plaques, infiltrated nodules, or leonine facies) and peripheral nerves (hypoesthesia, nerve enlargement) and presence of acid-fast bacilli on histopathology.
- Sarcoidosis – variable clinical presentation, yellow-brown "apple jelly" appearance of lesions on diascopy, frequent lung and eye involvement, and histopathology reveals "naked" noncaseating granulomas in the dermis or subcutaneous tissue; hypercalcemia and elevated serum ACE levels often present.
- Papular mucinosis (scleromyxedema) – characterized by grouped or widespread erythematous papules (large nodules not usually present) with histopathology revealing circumscribed deposits of abundant acid mucopolysaccharide between collagen bundles in superficial dermis.
- Juvenile xanthogranuloma (JXG) – nodules have more yellowish hue, there is no joint involvement, and histopathology reveals presence of foamy histiocytes and Touton giant cells.
- Generalized eruptive histiocytosis – characterized by recurrent crops of papules and nodules, typical distribution is trunk and upper extremities, no joint involvement, and histopathology findings similar to those of JXG except without foamy histiocytes.
- Progressive nodular histiocytosis – characterized by widespread nodules that can be quite large in size (up to 5 cm in diameter) but no joint involvement and histopathology findings similar to those of JXG.
- Xanthoma disseminatum – characterized by disseminated papules that frequently coalesce into larger plaques with predilection for flexural areas, no joint involvement, frequent association with diabetes insipidus, and histopathology similar to JXG.