MEDICAL CONDITIONS
Mixed Connective Tissue Disease
(MCTD) Medical Author: William C. Shiel, Jr., MD, FACP, FACR
What are connective tissues?
The connective tissues are the structural portions of our body that essentially hold the cells of the body together. These tissues form a framework or matrix for the body. The connective tissues are composed of two major structural molecules, collagen and elastin. There are many different collagen proteins that vary in amount in each tissue of the body. Elastin is another protein which has the capability of stretching and returning to original length like a spring. Elastin is the major component of ligaments (tissues which attach bone to bone).
Connective tissue diseases are disorders featuring abnormalities involving the collagen and elastin. Connective tissue diseases are often characterized by a variety of immune abnormalities that are common for each particular type of illness.
What diseases characteristically affect connective tissue?
Diseases of connective tissue which are strictly inheritable (due to genetic inheritance) include Marfan syndrome (can have tissue abnormalities in the heart, aorta, lungs, eyes, and skeleton), and Ehlers-Danlos syndrome (may have loose, fragile skin or loose [hyperextensible] joints depending on type).
Other diseases of connective tissue do not have specific gene abnormalities as their sole cause. These connective tissue diseases occur for unknown reasons. They are characterized as a group by the presence of spontaneous over activity of the immune system, which results in the production of unusual antibodies into the blood.
The classic immune-related connective tissue diseases include systemic lupus erythematosus , rheumatoid arthritis , scleroderma , polymyositis , and dermatomyositis. Each of these diseases has a characteristic presentation with typical findings that doctors can recognize during an examination. Each also has characteristic blood test abnormalities and abnormal antibody patterns. However, each of these diseases can evolve slowly or rapidly from very subtle abnormalities before demonstrating the classic features which help in the diagnosis. When these conditions have not developed the classic features of a particular disease doctors will often refer to the condition as "undifferentiated connective tissue disease." This implies that the characteristic features that are used to define the classic connective tissue disease are not present, but some symptoms or signs of connective disease exist. Individuals with undifferentiated connective tissue disease may never develop a fully definable condition or they may eventually develop a classic connective tissue disease.
What is mixed connective tissue disease?
Mixed connective tissue disease, as first described in 1972, is "classically" considered as an "overlap" of three diseases, systemic lupus erythematosus, scleroderma, and polymyositis. Patients with this pattern illness have features of each of these three diseases. They also typically have very high quantities of antinuclear antibodies (ANAs) and antibodies to ribonucleoprotein (anti-RNP) detectable in their blood. The symptoms of many of these patients eventually evolve to become dominated by features of one of three component illnesses, most commonly scleroderma features.
It is now known that overlap syndromes can occur that involve any combination of the connective tissue diseases. Therefore, for example, patients can have a combination of rheumatoid arthritis and systemic lupus erythematosus (hence, the coined name "rhupus").
How is MCTD diagnosed?
Today, true mixed connective tissue disease is diagnosed when patients demonstrate the clinical features (exam findings) of overlap illnesses (as described above) and have high amounts of the antibodies ANA and anti-RNP. MCTD patients do not typically have antibodies such as dsDNA, Scl70, which are particularly common in systemic lupus erythematosus and scleroderma respectively.
How is MCTD treated?
The treatment of mixed connective tissue disease is based on which features are causing symptoms. Therapies must be targeted for each of the organ systems affected. In general, treatment is often directed at suppressing the inflammation present in the tissues by using anti-inflammatory and immunosuppressive medications. These medications include nonsteroidal anti-inflammatory drugs (NSAIDs), cortisone drugs/steroids (such as prednisone ), antimalarial drugs ( hydroxychloroquine ), and cytotoxic drugs (such as methotrexate , azathioprine , and cyclophosphamide ). Organ damage, such as in the kidneys, can require additional treatments directed at high blood pressure , etc.
For the joint and muscle pains of MCTD, treatment options include NSAIDs, low-dose prednisone, hydroxychloroquine, and methotrexate can be helpful. Physical therapy for certain joints is sometimes helpful. For pulmonary hypertension , prednisone, angiotensin converting enzyme inhibitors, and cyclophosphamide are used. For interstitial lung disease, prednisone and cyclophosphamide are considered. To prevent damage to the kidneys, angiotensin converting enzyme inhibitors, such as captopril (Capoten), enalapril (Vasotec) are used, especially if blood pressure is elevated. Esophagus irritation and heartburn can be prevented by elevating the head of the bed and relieved with omeparazole (Prilosec) or lansoprazole (Prevacid). Antacids can also be helpful. Constipation , cramping and diarrhea is sometimes caused by bacteria that can be treated with tetracycline or erythromycin.
For Raynaud's phenomenon , patients are recommended to use hand and body warming techniques while protecting the fingers from injury. Nifedipine (Procardia), losartan (Cozaar, Hyzaar) and nitroglycerin cream are used to dilate the constricted blood vessels. Severe RP can lead to gangrene and the loss of digits. In rare cases of severe disease, nerve surgery called "sympathectomy" is sometimes considered. In order to prevent blood vessel spasming, the nerves that stimulate the constriction of the vessels (sympathetic nerves) are surgically interrupted. Usually this is performed during an operation that is localized to the sides of the base of the fingers at the hand. Through small incisions the tiny nerves around the blood vessels are stripped away. This procedure is referred to as a digital sympathectomy. - Connective tissues are the framework of the cells of the body.
- MCTD is an "overlap" combination of connective tissue diseases.
- Diagnosis of MCTD is supported by detecting abnormal antibodies in the blood.
- Treatment of MCTD is directed at suppressing immune-related inflammation of tissues.
For more specific information related to the individual connective tissue diseases, please read the following articles: Systemic Lupus Erythematosus , Rheumatoid Arthritis , Scleroderma , and Polymyositis.
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