Mixed connective tissue disease.

Three patients with mixed connective tissue disease (MCTD) had clinical features that included a high incidence of Raynaud phenomenon, arthritis, myositis, and swollen hands. The diagnostic laboratory test result was the presence of high titers of antibody to extractable nuclear antigen. These antibody titers are notably reduced or abolished in patients with MCTD when the tanned red blood cells that are used in the test are pretreated with ribonuclease. Speckled antinuclear antibodies were present in all patients. Patients with MCTD have a low incidence of renal disease, are responsive to treatment with prednisone, and have a good prognosis.