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Overview of Immunodeficiency Disorders
Immunodeficiency disorders involve malfunction of the immune system, resulting in infections that develop and recur more frequently, are more severe, and last longer than usual.
Immunodeficiency disorders usually result from use of a drug or from a long-lasting serious disorder (such as cancer) but occasionally are inherited.
People usually have frequent, unusual, or unusually severe or prolonged infections.
Doctors suspect immunodeficiency based on symptoms and do blood tests to identify the particular disorder.
People may be given antimicrobial drugs (such as antibiotics) to prevent and treat infections.
Immune globulin may be given if there are too few antibodies (immunoglobulins) or they are not functioning normally.
If the disorder is severe, stem cell transplantation is sometimes done.
Immunodeficiency disorders impair the immune system’s ability to defend the body against foreign or abnormal cells that invade or attack it (such as bacteria, viruses, fungi, and cancer cells). As a result, unusual bacterial, viral, or fungal infections or lymphomas or other cancers may develop. Another problem is that up to 25% of people who have an immunodeficiency disorder also have an autoimmune disorder (such as immune thrombocytopenia). In an autoimmune disorder, the immune system attacks the body's own tissue (see Autoimmune Disorders). Sometimes the autoimmune disorder develops before the immunodeficiency causes any symptoms.
There are two types of immunodeficiency disorders:
Primary: These disorders are usually present at birth and are usually hereditary. They typically become evident during infancy or childhood. There are more than 100 primary immunodeficiency disorders. All are relatively rare.
Secondary: These disorders generally develop later in life and often result from use of certain drugs or from another disorder, such as diabetes or human immunodeficiency virus (HIV) infection. They are more common than primary immunodeficiency disorders.
Some immunodeficiency disorders shorten life span. Others persist throughout life but do not affect life span, and a few resolve with or without treatment.
These disorders may be caused by mutations, sometimes in a specific gene. If the mutated gene is on the X (sex) chromosome, the resulting disorder is called an X-linked disorder (see Inheritance Patterns : X-Linked Inheritance). X-linked disorders occur more often in boys. About 60% of people with primary immunodeficiency disorders are male.
Primary immunodeficiency disorders are classified by which part of the immune system (see Overview of the Immune System) is affected:
Humoral immunity, which involves B cells (lymphocytes), a type of white blood cell that produces antibodies (immunoglobulins)
Cellular immunity, which involves T cells (lymphocytes), a type of white blood cell that helps identify and destroy foreign or abnormal cells
Both humoral and cellular immunity
Phagocytes (cells that ingest and kill microorganisms)
Complement proteins (proteins with various immune functions, such as killing bacteria and other foreign cells and making foreign cells easier for other immune cells to identify and ingest—see Innate Immunity : Complement System)
The affected component of the immune system may be missing, reduced in number, or abnormal and malfunctioning. Problems with B cells are the most common primary immunodeficiency disorders, accounting for more than half.
Some Primary Immunodeficiency Disorders
These disorders most commonly result from drugs (mainly immunosuppressants). Immunosuppressants are used to intentionally suppress the immune system. For example, some are used to prevent rejection of a transplanted organ or tissue (see Drugs Used to Prevent Transplant Rejection). They may be given to people with an autoimmune disorder to suppress the body's attack against its own tissues. Corticosteroids, a type of immunosuppressant, are used to suppress inflammation due to various disorders, such as rheumatoid arthritis. However, immunosuppressants also suppress the body’s ability to fight infections and perhaps to destroy cancer cells.
Chemotherapy and radiation therapy can also suppress the immune system, sometimes leading to immunodeficiency disorders.
Some Drugs That Can Cause Immunodeficiency
Disorders That Can Cause Immunodeficiency
Immunodeficiency disorders may result from almost any prolonged serious disorder. For example, diabetes can result in an immunodeficiency disorder because white blood cells do not function well when the blood sugar level is high. Human immunodeficiency virus (HIV) infection results in acquired immunodeficiency syndrome (AIDS), the most common severe acquired immunodeficiency disorder.
Undernutrition—whether of all nutrients or only one—can impair the immune system. When undernutrition causes weight to decrease to less than 80% of recommended weight, the immune system is often impaired. A decrease to less than 70% usually results in severe impairment.
People with an immunodeficiency disorder tend to have one infection after another. Usually, respiratory infections (such as sinus and lung infections) develop first and recur often. Most people eventually develop severe bacterial infections that persist, recur, or lead to complications. For example, sore throats and head colds may progress to pneumonia. However, having many colds does not necessarily suggest an immunodeficiency disorder.
Infections of the mouth, eyes, and digestive tract are common. Thrush, a fungal infection of the mouth, may be an early sign of an immunodeficiency disorder. Sores may form in the mouth. People may have chronic gum disease (gingivitis) and frequent ear and skin infections. Bacterial infections (for example, with staphylococci) may cause pus-filled sores to form (pyoderma). People with certain immunodeficiency disorders may have many large, noticeable warts (caused by viruses).
Many people have fevers and chills and lose their appetite and/or weight.
Abdominal pain may develop, possibly because the liver or spleen is enlarged.
Infants or young children may have chronic diarrhea and may not grow and develop as expected (called failure to thrive). Immunodeficiency may be more severe if symptoms develop in early childhood than if they develop later.
Other symptoms vary depending on the severity and duration of the infections.
Primary immunodeficiencies may occur as part of a syndrome with other symptoms. These other symptoms are often more easily recognized than those of the immunodeficiency. For example, doctors may recognize DiGeorge syndrome because affected infants have low-set ears, a small jawbone that recedes, and wide-set eyes.
Doctors must first suspect that an immunodeficiency exists. Then they do tests to identify the specific immune system abnormality.
Doctors suspect immunodeficiency when a person develops recurrent infections (typically sinusitis, bronchitis, middle ear infections, or pneumonia). Doctors also may suspect immunodeficiency when infections are severe or unusual or when a severe infection is caused by an organism that normally does not cause severe infection (such as Pneumocystis fungi or cytomegalovirus).
Results of a physical examination may suggest immunodeficiency and sometimes the type of immunodeficiency disorder. For example, doctors suspect certain types of immunodeficiency disorders when lymph nodes and tonsils are extremely small and other types when lymph nodes and tonsils are swollen and tender.
To help identify the type of immunodeficiency disorder, doctors ask at what age the person began to have recurring or unusual infections or other characteristic symptoms. Different types of immunodeficiency disorders are more likely depending on the age at which infections starts, as in the following:
The type of infection may also help doctors identify the type of immunodeficiency disorder. For example, knowing which organ (ear, lung, brain, or bladder) is affected, what the infecting organism is (bacteria, fungus, or virus), and what the organism's species is can help.
Doctors ask the person about risk factors, such as diabetes, use of certain drugs, exposure to toxic substances, and the possibility of having close relatives with immunodeficiency disorders (family history). The person may also be asked about past and current sexual activity, use of intravenous drugs, and previous blood transfusions to determine whether HIV infection could be the cause (see Human Immunodeficiency Virus (HIV) Infection).
Laboratory tests are needed to confirm the diagnosis of immunodeficiency and to identify the type of immunodeficiency disorder. A blood sample is taken and analyzed to determine the total number of white blood cells and the percentages of each main type of white blood cell. The white blood cells are examined under a microscope for abnormalities. Doctors also determine immunoglobulin levels, the number of red blood cells and platelets, and the levels of certain specific antibodies produced after the person is given vaccines. If any results are abnormal, additional tests are usually done.
Skin tests may be done if the immunodeficiency is thought to be due to a T-cell abnormality. The skin test resembles the tuberculin skin test, which is used to screen for tuberculosis. Small amounts of proteins from common infectious organisms such as yeast are injected under the skin. If a reaction (redness, warmth, and swelling) occurs within 48 hours, the T cells are functioning normally. No reaction could suggest a T-cell abnormality. Or doctors can check for T-cell abnormalities by doing blood tests to determine the number of T cells and to evaluate T-cell function.
People whose families are known to carry a gene for a hereditary immunodeficiency disorder may wish to have genetic testing to learn whether they carry the gene for the disorder and what their chances of having an affected child are. Talking with a genetic counselor before testing is helpful. Several immunodeficiency disorders, such as X-linked agammaglobulinemia, Wiskott-Aldrich syndrome, severe combined immunodeficiency, and chronic granulomatous disease, can be detected in a fetus by testing a sample of the fluid around the fetus (amniotic fluid) or the fetus’s blood (prenatal testing—see Procedures). Such testing may be recommended for people with a family history of an immunodeficiency disorder when the mutation has been identified in the family. Some experts recommend screening all newborns with a blood test that determines whether they have abnormal or too few T cells—called the T-cell receptor excision circles (TREC) test. This test can identify cellular immunity deficiencies, such as severe combined immunodeficiency. Identifying infants with severe combined immunodeficiency early can help prevent their death at a young age. TREC testing of all newborns is now required in many U.S. states.
Some of the disorders that can cause immunodeficiency can be prevented and/or treated, thus helping prevent immunodeficiency from developing. The following are examples:
HIV infection: Following safe sex guidelines and not sharing needles to inject drugs can reduce the spread of this infection. Also, antiretroviral drugs can usually treat HIV infection effectively (see Human Immunodeficiency Virus (HIV) Infection : Treatment).
Cancer: Successful treatment usually restores the function of the immune system unless people need to continue taking immunosuppressants.
Diabetes: Good control of blood sugar levels can help white blood cells function better and thus prevent infections.
Strategies for preventing and treating infections depend on the type of immunodeficiency disorder. For example, people who have an immunodeficiency disorder due to a deficiency of antibodies are at risk of bacterial infections. The following can help reduce the risk:
Being treated periodically with immune globulin (antibodies obtained from the blood of people with a normal immune system) given intravenously or under the skin
Practicing good personal hygiene (including conscientious dental care)
Not eating undercooked food
Not drinking water that may be contaminated
Avoiding contact with people who have infections
Antibiotics are given as soon as a fever or another sign of an infection develops and before surgical and dental procedures, which may introduce bacteria into the bloodstream. If a disorder (such as severe combined immunodeficiency) increases the risk of developing serious infections or particular infections, people may be given antibiotics to prevent these infections.
Antiviral drugs are given at the first sign of infection if people have an immunodeficiency disorder that increases the risk of viral infections (such as immunodeficiency due to a T-cell abnormality). These drugs include amantadine for influenza and acyclovir for herpes or chickenpox.
Vaccines are given if the specific immunodeficiency disorder does not affect antibody production. Vaccines are given to stimulate the body to produce antibodies that recognize and attack specific bacteria or viruses. If the person's immune system cannot make antibodies, giving a vaccine does not result in the production of antibodies and can even result in illness. For example, if a disorder does not affect production of antibodies, people with that disorder are given the influenza vaccine given once a year. Doctors may also give this vaccine to the person's immediate family members and to people who have close contact with the person. Generally, live-virus vaccines are not given to people who have a B- or T-cell abnormality because these vaccines may cause an infection in such people. Live-virus vaccines include rotavirus vaccines, measles-mumps-rubella vaccine, chickenpox (varicella) vaccine, varicella-zoster (shingles) vaccine, bacille Calmette-Guérin (BCG) vaccine, and influenza vaccine given as a nasal spray. A live-virus oral poliovirus vaccine is no longer used in the United States but is used in some other parts of the world.
Stem cell transplantation (see Stem Cell Transplantation) can correct some immunodeficiency disorders, particularly severe combined immunodeficiency. Stem cells are usually obtained from bone marrow but occasionally from blood (including umbilical cord blood). Stem cell transplantation, which is available at some major medical centers, is usually reserved for severe disorders.
Transplantation of thymus tissue is sometimes helpful. Gene therapy for a few congenital immunodeficiency disorders has been successful.
With appropriate treatment, many people with an immunodeficiency disorder have a normal life span. However, some require intensive and frequent treatments throughout life. Others, such as those with severe combined immunodeficiency, die during infancy unless they are given a bone marrow or stem cell transplant.
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