Definition:

Mixed connective tissue disease (MCTD) is a rare autoimmune disease characterized by a combination of clinical features of systemic lupus erythematosus, systemic sclerosis, and polymyositis with elevated antibodies to U1 small nuclear ribonucleoprotein (U1-RNP). The most common clinical manifestations of this disease are Raynaud's phenomenon, arthralgias, swollen joints, esophageal dysfunction, muscle weakness and fingers sausage-like appearance. The disease can be serious with development of pulmonary, kidney, cardiovascular, gastrointestinal, and central nervous system manifestations. The worst prognosis and high mortality are associated with the presence of pulmonary disease. Therapy should be individualised for each patient to address the specific organs involved and the severity of underlying disease activity. Inflammatory manifestations usually respond to steroid treatment, whereas clinical sclerodermatous manifestations such as sclerodactyly, and pulmonary interstitial disease more often require cytotoxic immunosuppressive treatment.