Mixed Connective Tissue Disease

Mixed connective tissue disease is a systemic autoimmune disease that shares clinical features with at least two other systemic autoimmune diseases, most often systemic sclerosis, lupus, polymyositis or dermatomyositis, and rheumatoid arthritis. It was first identified by Gordon Sharp in 1972 and is distinguished from a broader category called undifferentiated connective tissue disease by the presence of specific antibodies against the U1-RNP protein complex. Early symptoms include fatigue, low-grade fever, muscle pain, Raynaud phenomenon, swelling of the fingers and hands, joint pain, difficulty swallowing, and lung involvement, which affects roughly three-quarters of patients and can involve nearly every organ system. Long-term outcomes vary widely: about a third of patients go into remission with a favorable course, a third show moderate disease progression, and a third develop aggressive disease, with pulmonary hypertension the most serious and most often fatal complication. The disease predominantly affects women, who outnumber men by roughly eleven to sixteen to one.