What is mixed connective tissue disease (MCTD)?
Mixed connective tissue disease (MCTD) is a rare autoimmune disorder. An autoimmune disorder is one in which the immune system mistakenly views the body's own tissues as "invaders" and attacks them.
Mixed connective tissue disease has features of 3 other connective tissue diseases:
- Systemic lupus erythematosus (SLE): An inflammatory disease that can affect many different organs. Symptoms include fever, fatigue, joint pains, weakness, and skin rashes on the face, neck, and upper body.
- Scleroderma: Abnormal thickening and hardening of the skin, underlying tissue, and organs.
- Polymyositis: Muscle inflammation (swelling).
About 25% of patients with a connective tissue disease (such as dermatomyositis, rheumatoid arthritis, Sjogren's syndrome, and the 3 disease listed above), develop another connective tissue disease over the course of several years. This is known as an "overlap syndrome."
How common is mixed connective tissue disease (MCTD)?
MCTD is a rare disease, occurring most often in women in their 20s and 30s. Children can also be diagnosed with the disease.
Symptoms and Causes
What causes mixed connective tissue disease (MCTD)?
The causes of MCTD are not known. It is not directly inherited, although some research shows that the disease may occur more often in people with a family history of connective tissue disease. Exposure to certain viruses or chemicals such as polyvinyl chloride and silica are other possible causes.
What are the symptoms of mixed connective tissue disease (MCTD)?
In the beginning stages, patients who have MCTD have symptoms similar to those of patients with other connective tissue disorders, including:
- Muscle pain with no apparent cause.
- Joint pain.
- Low-grade fever.
- Raynaud phenomenon (reduced blood flow to the fingers, toes, ears, and nose, causing sensitivity, numbness, and loss of color in these areas).
Less common early symptoms may include:
- Severe polymyositis, often in the shoulders and upper arms.
- Acute (intense) arthritis.
- Aseptic meningitis (inflammation of the brain and spinal cord meninges, not caused by a bacteria or virus).
- Myelitis (inflammation of the spinal cord).
- Gangrene (death and decay) of fingers or toes.
- High fever.
- Abdominal pain.
- Neuropathy (nerve disorders) affecting the trigeminal nerve in the face.
- Hearing loss.
The "classic" symptoms of MCTD are:
- Raynaud phenomenon (see description above).
- Swollen "sausage-like" fingers, sometimes temporary but at other times progressing into sclerodactyly (thin fingers with hardened skin and limited movement).
- Inflamed joints and muscles.
- Pulmonary hypertension (high blood pressure in the blood vessels of the lungs).
Diagnosis and Tests
How is mixed connective tissue disease diagnosed (MCTD)?
A diagnosis can be difficult to make because the three conditions (SLE, scleroderma, and polymyositis) that can be seen in MCTD usually occur one after the other over a long period of time, rather than at the same time. It may take several years to make an accurate diagnosis of MCTD.
There are 4 features that point to MCTD rather than another connective tissue disorder:
- High concentrations in blood tests of a particular antibody called anti-U1-RNP (ribonucleoprotein).
- An absence of the severe kidney and central nervous system problems often found in SLE patients.
- Severe arthritis and pulmonary hypertension, which may not be found in either SLE or scleroderma patients.
- Raynaud phenomenon, and swollen hands or puffy fingers, which occur in only about 25% of SLE patients.
Management and Treatment
How is mixed connective tissue disease treated (MCTD)?
Treatment for MCTD must be tailored to each particular patient, depending on the organs that are affected and how severe the condition is. Some patients may need treatment only during flare-ups, while others may require constant care.
Treatment considerations include the following:
- Pulmonary hypertension is the most common cause of death in people with MCTD, and must be treated with antihypertensive medications.
- People with a mild form of MCTD may not need treatment, or only low doses of nonsteroidal anti-inflammatory drugs (such as ibuprofen and naproxen), antimalarials, or low-dose corticosteroids (such as prednisone) to treat inflammation.
- Higher doses of corticosteroids are often used to manage the signs and symptoms of moderate to severe MCTD. If major organs are affected, the patient may have to take immunosuppressants (to suppress the immune system).
- MCTD patients are also at risk of developing heart disease, including an enlarged heart or pericarditis (inflammation around the heart). Patients may need regularly scheduled electrocardiograms to monitor the heart's condition.
What can be expected following treatment for mixed connective tissue disease (MCTD)?
- Long-term use of steroids can lead to side effects such as bone loss due to osteoporosis, tissue death due to lack of blood flow, muscle weakness, and infections. Patients must see their doctor on a regular basis to monitor and control these possible effects.
- Women with MCTD who are thinking of becoming pregnant should first talk to their doctor. Pregnancy can increase flare-ups of the disease, and babies born to women with MCTD may suffer from low birth weight.
- Patients who have a long-term, incurable condition such as MCTD should develop ways of dealing with their disease. This includes seeking advice from medical and mental health professionals; proper diet and exercise (if not overly fatigued); learning as much as possible about the disease; and joining a chronic illness support group.
Can mixed connective tissue disease be prevented (MCTD)?
Since the causes of MCTD are not known, there is no way of preventing the disease.
Outlook / Prognosis
What is the long-term outlook for people with mixed connective tissue disease (MCTD)?
Since MCTD is comprised of a number of connective tissue disorders, there are many different possible outcomes, depending on the organs affected, the degree of inflammation, and how quickly the disease progresses. With proper treatment, 80% of people survive at least 10 years after diagnosis.