Mixed connective tissue disease has signs and symptoms of a combination of disorders — primarily lupus, scleroderma and polymyositis. For this reason, mixed connective tissue disease is sometimes referred to as an overlap disease.
In mixed connective tissue disease, the symptoms of the separate diseases usually don't appear all at once. Instead, they tend to occur in sequence over a number of years, which can make diagnosis more complicated.
Early signs and symptoms often involve the hands. Fingers might get puffy, and the fingertips become white and numb, often in response to cold exposure. In later stages, some organs — such as the lungs, heart and kidneys — may be affected.
There's no cure for mixed connective tissue disease. The signs and symptoms are usually treated with certain medications, such as prednisone.
Early indications of mixed connective tissue disease can include:
- General feeling of being unwell. This malaise may be accompanied by increased fatigue and a mild fever.
- Cold and numb fingers or toes (Raynaud's disease). In response to cold or stress, your fingers or toes might turn white and then purplish blue. After warming, the fingers or toes turn red.
- Swollen fingers or hands. Some people experience swelling of the fingers.
- Muscle and joint pain. Joints may become inflamed, swollen and deformed, similar to what occurs with rheumatoid arthritis.
- Rash. Red or reddish brown patches may appear over the knuckles.
When to see a doctor
See your doctor if you have signs and symptoms that interfere with your daily routine — particularly if you've already been diagnosed with lupus or another connective tissue disease.
The precise cause of mixed connective tissue disease isn't known.
Mixed connective tissue disease is an autoimmune disorder. In autoimmune disorders, your immune system — responsible for fighting off disease — mistakenly attacks healthy cells.
In connective tissue diseases, your immune system attacks the fibers that provide the framework and support for your body. Researchers are working to identify proteins produced by the immune system that might cause mixed connective tissue disease.
Some people with mixed connective tissue disease have a family history of the condition. But the role of genetics in causing the disease remains unclear.
Mixed connective tissue disease can occur in people of any age. However, it appears to be most common in women under the age of 50.
Mixed connective tissue disease can lead to serious complications, including:
- High blood pressure in the lungs (pulmonary hypertension). This condition is the main cause of death in people with mixed connective tissue disease.
- Interstitial lung disease. This large group of disorders can cause scarring in your lungs, which affects your ability to breathe.
- Heart disease. Parts of the heart may become enlarged, or inflammation may occur around the heart. Heart disease is the cause of death in about 20 percent of people with mixed connective tissue disease.
- Kidney damage. About one-fourth of people with mixed connective tissue disease develop kidney problems. Sometimes that damage can lead to kidney failure.
- Digestive tract damage. You may develop abdominal pain and problems with digesting food.
- Anemia. About 75 percent of people with mixed connective tissue disease have iron deficiency anemia.
- Tissue death (necrosis). People with severe Raynaud's disease can develop gangrene in the fingers.
- Hearing loss. In one small study, hearing loss was reported in almost half the patients with mixed connective tissue disease. More research is needed to understand this association.