Overlapping connective tissue disease

Overlapping connective tissue disease (also called overlap syndrome) is a condition in which a patient simultaneously or sequentially develops clinical features that meet criteria for two or more distinct autoimmune connective tissue diseases, but does not fit neatly into a single diagnosis such as systemic lupus erythematosus (SLE), systemic sclerosis (scleroderma), polymyositis/dermatomyositis, or rheumatoid arthritis. Unlike mixed connective tissue disease (MCTD), which is defined by the presence of anti-U1 RNP antibodies, overlapping connective tissue disease may present with various autoantibody profiles and does not require a specific serological marker. The condition reflects the shared immunopathological mechanisms among autoimmune connective tissue disorders. The disease can affect multiple body systems including the musculoskeletal system (arthritis, myositis, joint pain), skin (Raynaud's phenomenon, rashes, sclerodactyly), lungs (interstitial lung disease, pulmonary hypertension), kidneys (glomerulonephritis), heart (pericarditis, myocarditis), and the gastrointestinal tract (esophageal dysmotility). Patients may experience fatigue, fever, and constitutional symptoms. The specific clinical presentation depends on which connective tissue diseases overlap in a given individual, making the condition highly heterogeneous. Treatment is tailored to the specific organ manifestations and the component diseases present in each patient. Immunosuppressive therapies such as corticosteroids, methotrexate, azathioprine, mycophenolate mofetil, and cyclophosphamide are commonly used depending on disease severity and organ involvement. Biologic agents may also be employed. Management requires a multidisciplinary approach, and long-term monitoring is essential as the clinical phenotype may evolve over time, with new features of additional connective tissue diseases emerging during the disease course.

Data sourced from FDA regulatory filings and ClinicalTrials.gov. Updated periodically.

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