Rare rheumatologic disease

Orphanet code 182231 corresponds to mixed connective tissue disease (MCTD), also known as Sharp syndrome. MCTD is a rare systemic autoimmune rheumatologic disorder characterized by overlapping features of systemic lupus erythematosus (SLE), systemic sclerosis (scleroderma), polymyositis, and sometimes rheumatoid arthritis, combined with the presence of high titers of anti-U1 ribonucleoprotein (anti-U1 RNP) antibodies. The disease affects multiple body systems including the musculoskeletal system, skin, lungs, esophagus, and vascular system. Key clinical features include Raynaud's phenomenon (often the earliest symptom), swollen or "puffy" hands, arthritis or arthralgias, myositis with muscle weakness, esophageal dysmotility, sclerodactyly, and pulmonary involvement including interstitial lung disease and pulmonary arterial hypertension. Pulmonary arterial hypertension is the most serious complication and a leading cause of mortality. Other manifestations may include serositis (pleuritis or pericarditis), lymphadenopathy, skin rashes, and hematologic abnormalities. The disease predominantly affects women, with a female-to-male ratio of approximately 9:1. There is no cure for MCTD, and treatment is tailored to the specific organ systems involved and disease severity. Mild disease may be managed with nonsteroidal anti-inflammatory drugs (NSAIDs), hydroxychloroquine, or low-dose corticosteroids. More severe manifestations such as myositis, significant organ involvement, or vasculitis may require higher-dose corticosteroids and immunosuppressive agents such as methotrexate, azathioprine, mycophenolate mofetil, or cyclophosphamide. Calcium channel blockers and other vasodilators are used for Raynaud's phenomenon. Pulmonary arterial hypertension requires specific targeted therapies. Regular monitoring for disease progression, particularly pulmonary and cardiac complications, is essential for long-term management.

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