Snapshot A 29-year-old woman presents with general malaise, myalgias, and low-grade fever. She also reports the tips of her fingers turn blue after touching a cold object, which subsequently returns to its baseline color when the cold object is no longer touched. On physical exam, there is a malar rash, swelling of the digits, and joint tenderness. Laboratory testing is positive for anti-nuclear antibodies (ANA) and anti-U1 RNP antibodies. Introduction Clinical definition generalized connective tissue disorder with clinical features of systemic lupus erythematosus, systemic sclerodermia, and polymyositis along with high levels of anti-U1-RNP antibodies Epidemiology Demographics more common in women 15-25 years of age but can occur at any age ETIOLOGY Pathophysiology pathobiology autoimmune disease Presentation Symptoms Raynaud's phenomenon arthralgia arthritis myositis sclerodactyly hand swelling Imaging Echocardiography indications for early diagnosis of pulmonary arterial hypertension and for the evaluation of valvular disease Studies Labs positive for anti-U1-RNP antibodies Differential Systemic lupus erythematosus (SLE) Scleroderma Polymyositis Rheumatoid arthritis Idiopathic pulmonary arterial hypertension DIAGNOSIS Diagnostic criteria clinical diagnosis supported by anti-U1-RNP antibodies on serology Treatment Treatment is aimed at controlling symptoms and is targeted at organ involvement Medical prednisone indications responsive in patients presenting with symptoms consistent with SLE in patients with fatigue, myositis, myalgias, arthralgias, pleuritis, pericarditis, autoimmune anemia, and thrombocytopenia calcium channel blockers indications pulmonary arterial hypertension Raynaud's phenomenon Complications The major cause of death is pulmonary hypertension in MCTD Prognosis Generally a favorable outcome