Mixed connective tissue disease is a term used by some doctors to describe a systemic rheumatic disease characterized by overlapping features of systemic lupus erythematosus, systemic sclerosis, and polymyositis.
Raynaud syndrome, joint pains, various skin abnormalities, muscle weakness, and problems with internal organs can develop.
The diagnosis is based on symptoms and the results of blood tests to detect levels of characteristic antibodies.
Mixed connective tissue disease is more common among women than men. It occurs worldwide, affects people of all races, and often peaks in incidence during adolescence.
The cause of mixed connective tissue disease is unknown, but it is an autoimmune disease. In an autoimmune disease, antibodies or cells produced by the body attack the body’s own tissues.
Symptoms of MCTD
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The typical symptoms of mixed connective tissue disease are Raynaud syndrome (in which the fingers suddenly become very pale and tingle or become numb or blue in response to cold or emotional upset), joint inflammation (arthritis), swollen hands, muscle weakness, heartburn, and shortness of breath. Raynaud syndrome may precede other symptoms by many years. Regardless of how mixed connective tissue disease starts, it tends to worsen, and symptoms spread to several parts of the body.
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Lupus-like rashes may develop. Skin changes similar to those of systemic sclerosis also may occur, such as tightening of the finger skin and sores on the fingertips.
Almost everyone with mixed connective tissue disease has aching joints. Approximately 75% of people develop the swelling and pain typical of arthritis. Mixed connective tissue disease damages the muscle fibers, so the muscles may feel weak and sore, especially in the shoulders and hips. Tasks such as lifting the arms above the shoulders, climbing stairs, and getting out of a chair can become very difficult.
The lungs are affected in up to 75% of people with mixed connective tissue disease. Fluid may collect around the lungs (pleural effusion). Interstitial lung disease, which affects the air sacs of the lungs, can be the most serious problem because it can cause shortness of breath. Pulmonary hypertension, a condition in which blood pressure in the arteries of the lungs (the pulmonary arteries) is abnormally high, is a major cause of death.
Disorders that cause inflammation in the heart, such as pericarditis and myocarditis, can develop. Rarely, the heart is weakened, leading to heart failure. Symptoms of heart failure may include fluid retention, shortness of breath, and fatigue.
The kidneys are affected in approximately 25% of people, and the damage is usually mild compared to the damage caused by lupus.
Other symptoms may include fever, swollen lymph nodes, and abdominal pain.
Sjögren syndrome may develop. Over time, many people develop symptoms that are more typical of lupus or systemic sclerosis.
Diagnosis of MCTD
Blood tests
Sometimes other tests
The diagnosis of mixed connective tissue disease is based on all of the information doctors gather, including symptoms, physical examination results, and all test results.
Doctors suspect mixed connective tissue disease when symptoms of lupus, systemic sclerosis, and polymyositis overlap.
Blood tests are done to detect levels of antinuclear antibodies (ANA) and an antibody to ribonucleoprotein (RNP), which are present in most people who have mixed connective tissue disease. People who have a high level of these antibodies but who do not have other antibodies present in similar disorders are most likely to have the disease. Although blood test results can help doctors diagnose the disease, they alone cannot confirm a definite diagnosis of mixed connective tissue disease because sometimes the abnormalities they detect are present in healthy people or in people who have other disorders.
To determine whether people have pulmonary hypertension, doctors do pulmonary function testing to assess the lungs and echocardiography to assess the heart. If doctors suspect other organs are affected, they may do other tests, such as magnetic resonance imaging (MRI) or a muscle biopsy (removal of a piece of muscle tissue for examination and testing), to detect problems.
Treatment of MCTD
Nonsteroidal anti-inflammatory drugs, antimalarials, or very low doses of corticosteroids for mild illness
Corticosteroids and other immunosuppressants for moderate to severe illness
Other treatments as needed for other symptoms
The treatment of mixed connective tissue disease is similar to that of lupus, systemic sclerosis, and idiopathic inflammatory myopathy. Corticosteroids (a type of immunosuppressant) are usually effective, especially when the disease is diagnosed early.
People who have more severe disease are given higher doses of corticosteroids. People whose major organs are severely affected usually require higher doses of corticosteroids and additional immunosuppressants.
People who develop myositis or systemic sclerosis
People who take corticosteroids are at risk of fractures related to osteoporosis. To prevent osteoporosis, these people are given the medications used to treat osteoporosis, such as bisphosphonates and .
People who are receiving immunosuppressants are also given medications to prevent infections such as by the fungus Pneumocystis jirovecii (see prevention of pneumonia in people with a weakened immune system) and vaccines against common infections such as pneumonia, influenza, and COVID-19.
People who have mixed connective tissue disease are at increased risk of atherosclerosis, are closely monitored by doctors, and are treated for specific symptoms and complications of atherosclerosis as they occur.
Doctors monitor people with mixed connective tissue disease for pulmonary hypertension by doing pulmonary function testing, echocardiography, or both every 1 to 2 years, depending on symptoms.
Prognosis for MCTD
Overall, the 10-year survival rate is approximately 96%, but the prognosis depends largely on a person's symptoms. For example, the prognosis is worse for people who have mainly symptoms of systemic sclerosis and polymyositis.
Causes of death include pulmonary hypertension, kidney failure, infection, and heart disease.
