Mixed Connective
Tissue Disease (MCTD)
By Alana
M. Nevares, MD, Assistant Professor, Division of Rheumatology and Clinical
Immunology , Robert Larner, MD, College of Medicine, The University of Vermont
Medical Center
Autoimmune
Disorders of Connective Tissue
Mixed Connective Tissue
Disease (MCTD)
Raynaud
phenomenon, 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.
Treatment
varies depending on the severity of symptoms and may include nonsteroidal
anti-inflammatory drugs, hydroxychloroquine,
corticosteroids, immunosuppressive drugs, or a combination.
Mixed
connective tissue disease is more common among women than men. Mixed connective
tissue disease occurs worldwide and affects people of all ages, often peaking
in incidence during adolescence and the 20s. The cause of mixed connective
tissue disease is unknown, but it is an autoimmune disease.
Mixed
connective tissue disease is considered an overlap disease because the symptoms
of mixed connective tissue disease overlap with those of other autoimmune
diseases of connective tissue so much that sometimes doctors cannot make a
distinction. However, not everyone who has mixed connective tissue disease
develops symptoms of the other autoimmune diseases.
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, difficulty swallowing, heartburn, and shortness of breath. Raynaud
phenomenon 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.
Lupus-like
rashes may develop. Skin changes similar to those of systemic sclerosis also
may occur, such as tightening of the finger skin. The hair may thin.
Almost
everyone with mixed connective tissue disease has aching joints. About 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 in or around the lungs. In some people, abnormal lung
function is the most serious problem, causing shortness of breath during
exertion. Interstitial lung diseases, which affect the
tissue around the air sacs of the lungs (alveoli), are the most common lung
problems. 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.
Occasionally,
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 about 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 lupusor systemic sclerosis.
Blood
tests
Sometimes
other tests
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 mixed connective tissue disease. Although blood test results can help
doctors diagnose mixed connective tissue 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. 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.
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.
Prognosis
Despite
treatment, mixed connective tissue disease worsens in about 13% of the people,
causing potentially fatal complications. Causes of death include pulmonary
hypertension (mainly) and heart disease. The prognosis is worse for people who
have mainly features of systemic sclerosis or polymyositis.
Mixed
connective tissue disease does not appear to shorten life expectancy, except
for people who have certain features, such as those of systemic sclerosis,
polymyositis, pulmonary hypertension, or heart disease.
Treatment
Nonsteroidal
anti-inflammatory drugs, hydroxychloroquine,
or very low doses of corticosteroids for mild illness
Corticosteroids
and immunosuppressive drugs 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 autoimmune myositis. Corticosteroids are usually
effective, especially when the disease is diagnosed early. Mild cases can be
treated with nonsteroidal anti-inflammatory drugs (NSAIDs), hydroxychloroquine or similar drugs, or
very low doses of corticosteroids. The more severe the disease, the higher the
dose of corticosteroid needed. In moderate to severe cases, immunosuppressive
drugs (such as azathioprine, methotrexate, or mycophenolate mofetil) may
also be needed. People whose major organs are severely affected usually require
higher doses of corticosteroids and additional immunosuppressive drugs.
In
general, the more advanced the disease and the greater the organ damage, the
less effective the treatment. Systemic sclerosis–like damage to the skin and
esophagus is least likely to respond to treatment.
People
who develop myositis or systemic sclerosis are treated based on
their symptoms. People who have Raynaud phenomenon are treated based on their
symptoms and may be given a calcium channel blocker (such as nifedipine) and drugs that increase blood
flow (such as sildenafil or tadalafil).
People
who take corticosteroids are at risk of fractures related to osteoporosis. To prevent osteoporosis, these
people are given the drugs used to treat osteoporosis, such as bisphosphonates and supplemental vitamin D and calcium. People who
are receiving immunosuppressants are also given drugs to prevent infections
such as by the fungus Pneumocystis jirovecii (see prevention of pneumonia in immunocompromised people).
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
may continue to 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.
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