What is mixed connective tissue disease (MCTD)?
Mixed connective tissue disease, as first described in 1972, is "classically" considered an "overlap" of three diseases, systemic lupus erythematosus, scleroderma, and polymyositis. Patients with this pattern of 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. Mixed connective tissue disease is often abbreviated as MCTD.
It is now known that overlap syndromes can occur that involve any combination of connective tissue diseases. Therefore, for example, patients can have a combination of rheumatoid arthritis and systemic lupus erythematosus (hence, the coined name "rhupus").
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. Many different collagen proteins vary in amount in each tissue of the body. Elastin is another protein that has the capability of stretching and returning to its original length like a spring. Elastin is the major component of ligaments (tissues that attach bone to bone).
- Connective tissue diseases are disorders featuring abnormalities involving 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 affect connective tissue?
Diseases of connective tissue that 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). Pseudoxanthoma elasticum is an inherited disorder of elastin.
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 overactivity of the immune system, which results in the production of unusual antibodies in the blood.
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 clinical 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 that 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 are causes of mixed connective tissue disease?
The most significant causes and risk factors for developing mixed connective tissue disease are certain gene patterns that are inherited from ancestors. There is no known environmental toxin that has been shown to cause mixed connective tissue disease.
What are the symptoms of mixed connective tissue disease?
The signs and symptoms of mixed connective tissue disease vary greatly from one individual affected to another.
- If polymyositis is the dominant feature, muscle weakness is prominent.
- If systemic lupus erythematosus prevails, there may be chest pain with breathing, kidney disease, and/or arthritis of the joints.
- If scleroderma symptoms dominate, there can be diffuse swelling and thickening of the fingers and feet with bluish discoloration of the fingers after cold exposure (Raynaud's phenomenon).
Diagnosis of mixed connective tissue disease
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 in their blood. Mixed connective tissue disease patients do not typically have antibodies such as dsDNA and Scl70, which are particularly common in systemic lupus erythematosus and scleroderma respectively.
Doctors who treat patients with mixed connective tissue disease include primary-care providers such as general practitioners, internists, and family medicine doctors. Other specialists who can be involved in the care of these patients include neurologists, cardiologists, pulmonologists, and nephrologists. Specialists with a particular interest in mixed connective tissue disease are rheumatologists.
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What are the treatments for mixed connective tissue disease?
The treatment of mixed connective tissue disease is based on which features are causing symptoms and signs. The prognosis (outlook) varies accordingly. 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.
Joint and Muscle Pains
For the joint and muscle pains of mixed connective tissue disease, treatment options include:
- Low-dose prednisone
Sometimes TNF blockers infliximab (Remicade), etanercept (Enbrel), or adalimumab (Humira) are considered for inflammatory arthritis. Physical therapy for certain joints is sometimes helpful.
For pulmonary hypertension, medications that tend to open the arteries to the lungs are used along with blood-thinning drugs and even supplemental oxygen.
Interstitial Lung Disease
For interstitial lung disease, prednisone and cyclophosphamide are considered.
- Angiotensin-converting enzyme inhibitors, such as captopril (Capoten) and enalapril (Vasotec), are used to prevent damage to the kidneys, especially if blood pressure is elevated.
- Esophagus irritation and heartburn can be prevented by elevating the head of the bed and can be relieved with omeprazole (Prilosec) or lansoprazole (Prevacid). Antacids can also be helpful.
- Constipation, cramping, and diarrhea are 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.
- To prevent blood vessel constriction, 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 digital sympathectomy.
Gastroesophageal reflux disease in mixed connective tissue disease can be helped by elevation of the head of the bed and taking stomach acid-blocking medications. Raynaud's phenomenon can be helped by general body warming and wearing gloves to prevent chilling.
What is the prognosis for mixed connective tissue disease?
The outlook for mixed connective tissue disease very much depends on the location and intensity of the organs affected. Those who are treated and monitored early tend to have better outcomes.
Is it possible to prevent mixed connective tissue disease?
No. There is no prevention for mixed connective tissue disease.
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Top Mixed Connective Tissue Disease Related Articles
Antinuclear Antibody TestAntinuclear antibodies (ANAs), unusual antibodies that can bind to certain structures within the nucleus of the cells, are found in patients whose immune system may be predisposed to cause inflammation against their own body tissues. ANAs are indicative of the potential presence of an autoimmune illness.
Arthritis (Joint Inflammation)Arthritis is inflammation of one or more joints. When joints are inflamed they can develop stiffness, warmth, swelling, redness and pain. There are over 100 types of arthritis, including osteoarthritis, rheumatoid arthritis, ankylosing spondylitis, psoriatic arthritis, and gout.
Chest X-RayChest X-Ray is a type of X-Ray commonly used to detect abnormalities in the lungs. A chest X-ray can also detect some abnormalities in the heart, aorta, and the bones of the thoracic area. A chest X-ray can be used to define abnormalities of the lungs such as excessive fluid (fluid overload or pulmonary edema), fluid around the lung (pleural effusion), pneumonia, bronchitis, asthma, cysts, and cancers.
Connective Tissue (CT) DiseaseConnective tissue disease is when the body's connective tissues come under attack, possibly becoming injured by inflammation. Inherited connective tissue diseases include Marfan syndrome and Ehlers-Danlos syndrome. Systemic lupus erythematosus, rheumatoid arthritis, scleroderma, polymositis, and dermatomyositis are examples of connective tissue diseases that have no known cause.
GangreneGangrene may result when blood flow to a tissue is lost or not adequate to keep the tissue alive. There are two types of gangrene: wet and dry. All cases of wet gangrene are infected by bacteria. Most cases of dry gangrene are not infected. If wet gangrene goes untreated, the patient may die of sepsis within hours or days. Dry gangrene usually doesn't cause the patient to die. Symptoms of dry gangrene include numbness, discoloration, and mummification of the affected tissue. Wet gangrene symptoms include swelling, pain, pus, bad smell, and a black appearance of the affected tissue. Treatment depends upon the type of gangrene and how much tissue is compromised by the gangrene.
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ScleritisScleritis is inflammation of the white part of the eye. It may be caused by a serious underlying condition, such as an autoimmune disease. Symptoms include redness, pain, tearing, sensitivity to light, and decreased visual acuity. Treatment may include eyedrops as well as treatment for any underlying disease process. Scleritis cannot be prevented.
SclerodermaScleroderma is an autoimmune disease of the connective tissue. It is characterized by the formation of scar tissue (fibrosis) in the skin and organs of the body, leading to thickness and firmness of involved areas. Scleroderma is also referred to as systemic sclerosis, and the cause is unknown. Treatment of scleroderma is directed toward the individual features that are most troubling to the patient.
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