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Auto-immune diseases are caused by a malfunction of the immune system. While our bodies normally recognise a harmful 'foreign invader' and produce antibodies to fight it, in an auto-immune disease the body is unable to distinguish between foreign invaders and the body's own tissue. The result is the production of antibodies which fight the body's own tissue as well as the foreign invader.
The body produces a small number of self-hostile lymphocytes which would normally be 'policed' and destroyed by other lymphocytes. However, the process may be disrupted by various triggers, allowing the numbers of self-hostile lymphocytes to increase.
It is thought that almost any virus, certain bacteria such as streptococci, or drugs (such as methyldopa) may play a part in triggering an auto-immune process in someone who already has a genetic pre-disposition.
There are two classes of auto-immune disorders: organ-specific (eg Hashimoto's thyroiditis) and non-organ specific (eg rheumatoid arthritis).
It is possible for some patients to experience organ specific and non-organ specific diseases simultaneously, and a person suffering from one auto-immune disease is more likely to develop another than a non-sufferer, although this is not always the case.
Organ-specific auto-immune disease is usually treated with replacement therapy, eg replacement thyroxine for Hashimoto's thyroiditis.
In cases of non-organ specific disease the treatment often involves reducing the activity of the immune system, a delicate adjustment which normally involves treating the patient with corticosteroid drugs.
Steroid therapy is not without dangers. While these drugs often have a rapid effect, patients must be closely monitored and the side effects may be unpleasant. These include: weight gain, osteoporosis, hypertension and increased risk of diabetes and infection.
In the more severe cases treatment may involve the use of immuno-suppressant drugs such as cyclophosphamide, methotrexate or azathioprine. Since these drugs may also damage rapidly dividing tissues, such as bone marrow, their use must be monitored.
Other treatment options include total lymph node irradiation. Most lymphocytes are very sensitive and easily damaged by x-rays. Such treatment reduces the number of lymphocytes in the blood and alters the immune system's interactions and responses to antigens.
Patients undergoing this treatment also suffer side effects including fatigue, loss of appetite, diarrhoea, weight loss and occasionally shingles.
In view of the severity of some of the after-effects, this therapy is usually restricted to younger people (under 50 years of age) who are in reasonably good health, and/or to people who have one of the more severe auto-immune diseases (eg lupus or rheumatoid arthritis), and who have failed to respond to other forms of treatment.
Insulin-dependent diabetes mellitus (IDDM) or Type 1 is an organ-specific type of auto-immune disease caused by a deficiency of insulin. This is due to the auto-immune destruction of pancreatic beta cells which usually begins between ten and 20 years of age. Treatment is usually by injecting insulin.
Non-insulin dependent diabetes mellitus (NIDDM) or Type 2 diabetes is not thought to be auto-immune in origin.
The following are examples of organ-specific auto-immune diseases.
Hashimoto's thyroiditis or (myxodoema) is associated with chronic inflammation of the thyroid gland with an under-production of thyroxine. It usually occurs in middle life. The main symptoms are severe lethargy, dry skin and hair, and damage to the nerves in the limbs. More women suffer from the disease than men in a ratio of five to one. Treatment is long-term replacement using thyroxine tablets.
Graves' disease is associated with overactivity of the thyroid gland. Antibodies bind to and stimulate hormone receptors on the surface of the gland, increasing its production of thyroxine.
People with Graves' disease often have protruding eyeballs, suffer weight loss, anxiety, tremor of the hands and have a fast pulse. Sufferers are usually women in their 40s and the ratio of female to male sufferers is seven to one.
Graves' disease is treated by controlling the overactive gland with anti-thyroid drugs, radioactive iodine, surgery or a combination of these.
Multiple sclerosis (MS) is a progressive disease of the central nervous system in which scattered patches of myelin in the brain and spinal cord are destroyed. This leads to various neurological defects such as impaired vision, unsteadiness of the limbs and loss of feeling or tingling of various parts of the body.
The severity of the disease varies from person to person, with periods of remission occurring in some patients who are able to live normal lives for much of the time.
MS is the most commonly acquired disease of the nervous system in young adults. The incidence is one in 1,000 people. It is more common in young females the ratio of women to men affected being three to two. There appears to be a genetic factor involved since relatives of affected people are eight times more likely to contract this disease.
MS is treated in various ways. Corticosteroids may shorten the duration of an acute attack, while intensive immuno-suppressive therapy using drugs such as azathioprine, cyclophosphamide or antilymphocyte globulin may be used with drugs used to control specific symptoms such as depression or incontinence.
In the past two decades there have been a number of breakthroughs in molecular biology, and research continues into the use of beta-interferon in the treatment of life-threatening viral infections, particularly in people who have immunodeficiency disorders.
Interferons are naturally occurring proteins which have complex effects on immunity and cell function. Interferon-beta is licensed for use in patients with relapsing remitting MS who are able to walk unaided. However, not all patients respond to treatment. It is also licensed for use in the treatment of secondary progressive MS.
Myasthenia gravis is a comparatively rare auto-immune disorder, manifesting as a progressive muscular weakness which can occur at any time of life. It is closely related to thyrotoxicosis and is associated with diabetes mellitus, rheumatoid arthritis and systemic lupus erythematosus.
About two to five new cases per 100,000 people are diagnosed annually in the UK. Again, it occurs more frequently in women than men in a ratio of three to two.
The eye muscles are often the first to be affected: sufferers have drooping eyelids and may suffer double vision. The muscles of the face, throat, larynx and neck become weak, often resulting in difficulty in breathing, speaking, chewing and swallowing. Weakness of the muscles of the arms or legs makes simple tasks like combing the hair or going up stairs difficult.
It has been found that abnormalities of the thymus gland are present in 75 per cent of myasthenia gravis sufferers, and in 10 per cent of these a form of tumour of the thymus gland develops. It is thought that the initial abnormal response in myasthenia gravis may be against acetylcholine receptors on epithelial cells in the thymus causing cross reactivity between the acetylcholine receptors in the thymus and muscles.
Myasthenia gravis is treated by using drugs which block the action of cholinesterase an enzyme which usually destroys acetylcholine in the body. Drugs used include neostigmine, distigmine, and pyridostigmine. Occasionally high doses of steroids or azathioprine may be used to block the immune process when treating myasthenia gravis.
Myositis is a disorder occasionally found in people aged 40 and 60. It causes weakness of the muscles, particularly those involved in movement of the shoulders and hips and affects three times as many women as men. Inflammation and destruction of muscle occurs which may be treated with steroids or with drugs to suppress the immune system.
Dermatomyositis is similar to myositis and is caused by inflammation of the muscles and skin.
The first sign of this disorder is often a red rash over the bridge of the nose and cheeks, followed by a red rash on the knees, elbows and knuckles. This is followed by a weakness of the muscles of the shoulders and pelvis which later become stiff and painful.
Treatment is usually with corticosteroid drugs, and/or immunosuppressant drugs. About half the cases recover over a few years. In most of the remaining sufferers the disease persists with continuing stiffness of muscles.
Vitiligo is an auto-immune disorder in which patches of the skin lose their colour due to an absence of melanocytes the cells which produce the pigment melanin. This disorder occurs at any age and affects approximately one in 200 people. In about 30 per cent of sufferers a spontaneous re-pigmentation occurs. Treatment may be by phototherapy using PUVA, or by the use of corticosteroid creams which assists re-pigmentation. The use of make up to disguise the affected areas may also be helpful.
Pernicious anaemia is a relatively common disease in middle aged women and may develop over two to three years. The development of antibodies to some of the cells of the stomach lining affect the production of the intrinsic factor needed to assist in the absorption of vitamin B12. Patients suffering from pernicious anaemia become pale, tired and weak as the disease progresses, their red blood cells become enlarged, they often suffer a sore mouth and develop weakness of the hands and feet. In severe cases there may be breathlessness, chest pain and loss of balance due to the damage to the nervous system.
Pernicious anaemia is usually treated successfully with regular injections of hydroxocobalamin intramuscularly every two to three months for the rest of the patient's life.
Systemic lupus erythematosus is a classic auto-immune disorder mainly affecting women in their childbearing years. The disease may be inherited and hormonal changes may trigger its development. Certain drugs are also thought to have an effect on its development, eg hydralazine, procainamide and isoniazid.
The most common symptoms include skin rashes, joint pain and fatigue. The skin rashes usually appear on areas exposed to light and may vary from small red patches to large blisters. Pain in the joints may be accompanied by slight swelling or inflammation around the tendons. If there is a build up of fluid in the tissues around the heart or lungs, patients may suffer shortness of breath.
Treatment of milder symptoms of lupus includes the use of non-steroidal or anti-malarial drugs. In more serious cases where problems occur with the heart, lungs, kidneys, blood cells or central nervous system, steroids may be used sometimes with azathioprine and cyclophosphamide.
Patients suffering from rheumatoid arthritis have a rheumatoid factor in their blood. This is an antibody that binds to part of another human immunoglobin.
Some forms of the disease are self-limiting and mild, but others may cause severe deformities. Non-steroidal anti-inflammatory drugs are used to relieve the pain and stiffness in the joints. Anti-rheumatic drugs such as penicillamine or gold may be used to slow the progress of the disease, but their use might be limited in some patients because of the side effects such as liver damage, bone marrow suppression and rashes.
Immunosuppressant drugs corticosteroids or azathioprine may be used to suppress the body's immune system if anti-rheumatic drugs fail to provide relief.
Acquired immune deficiency syndrome (AIDS) is caused by the human immunodeficiency virus (HIV). HIV may trigger a range of auto-immune type symptoms, eg, lupus-type symptoms including kidney inflammation and skin rash, or features of polymyositis and rheumatoid arthritis. Also thyroid disease, diabetes and MS together with most other auto-immune diseases have been reported in patients suffering from AIDS.
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January modules
Heroin (module 1149) and questionnaire
Auto-immune deficiency (module 1150) and questionnaire
Adverse drug reactions (module 1151) and questionnaire
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