Mixed connective tissue disease (MCTD) is a rare autoimmune disorder that is characterized by features commonly seen in three different connective tissue disorders: systemic lupus erythematosus, scleroderma, and polymyositis. Some affected people may also have symptoms of rheumatoid arthritis. Although MCTD can affect people of all ages, it appears to be most common in women under age 30. Signs and symptoms vary but may include Raynaud's phenomenon; arthritis; heart, lung and skin abnormalities; kidney disease; muscle weakness, and dysfunction of the esophagus. The cause of MCTD is currently unknown.

Treatment may include medications such as nonsteroidal anti-inflammatory drugs (NSAIDs), corticosteroids and immune-suppressing drugs to help manage symptoms.

• Accumulation of fluid in the tissue of the hands that causes puffiness and swelling (edema)
• Skin findings including lupus-like rashes (including reddish brown patches), reddish patches over the knuckles, violet coloring of the eyelids, loss of hair (alopecia), and dilation of small blood vessels around the fingernails (periungual telangiectasia)
• Dysfunction of the esophagus (hypomotility)
• Abnormalities in lung function which may lead to breathing difficulties, and/or pulmonary hypertension
• Heart involvement (less common in MCTD than lung problems) including pericarditis, myocarditis, and aortic insufficiency
• Kidney disease
• Neurologic abnormalities (in about 10 percent of people with MCTD) such as blood vessel narrowing causing "vascular" headaches; a mild form of meningitis; seizures; blockage of a cerebral vessel (cerebral thrombosis) or bleeding; and/or various sensory disturbances in multiple areas of the body (multiple peripheral neuropathies)
• Anemia and leukopenia (in 30 to 40 percent of cases)
• Lymphadenopathy, enlargement of the spleen (splenomegaly), enlargement of the liver (hepatomegaly), and/or intestinal involvement in some cases

There is currently no cure for mixed connective tissue disease (MCTD). However, treatments can help manage symptoms of the condition. For example, medications such as over-the-counter or prescription nonsteroidal anti-inflammatory drugs may help with inflammation and pain of the muscles or joints. Glucocorticoids may be recommended in certain situations, such as during disease flares or when complications arise (e.g., aseptic meningitis, myositis, pleurisy, pericarditis, and myocarditis). Some people with MCTD require long term use of immunosuppressant medications.

Additional medications may be prescribed based on the signs and symptoms present in each person. For example, if a person with MCTD has developed symptoms similar to those of lupus, medications typically prescribed for people with lupus may be recommended.