Patients with immunodeficiency diseases have undue susceptibility to infection. This can mean (1) too many infections, (2) unusually severe infections, (3) infections without a symptom-free period, (4) infections with unusual organisms (Giardia, Pneumocystis), (5) undue complications from infections, and (6) poor response to treatment. Many patients with immunodeficiency must take continuous antibiotics to remain free of infection.
Not all patients with increased susceptibility to infection have immunodeficiency. A host of systemic illnesses can cause infection and mimic immunodeficiency (Table 4). When these disorders are excluded, a defect in the immune system must be suspected. Some of these immunodeficiencies are hereditary or genetic and appear in infancy. More commonly, the immunodeficiency is secondary, due to the presence of some other illness or condition that temporarily impairs the immune system. These may be 20 to 30 times more common than primary immunodeficiency. Indeed, the leading cause of childhood death is the immunodeficiency of malnutrition, leading to severe and often fatal infectious complications.
A secondary immunodeficiency is usually reversible if the cause is removed. A notable exception is AIDS, which leads to permanent T cell impairment. Immunodeficiencies are classified based on the location of the immune defect. Accordingly, we recognize antibody deficiency or В cell defects, cellular or T cell defects, phagocytic cell defects, and complement defects.
Patients with immunodeficiency have some characteristic clinical features. Almost all have had one or more severe bacterial infections, failure to thrive (in infants), and persistent malaise (in adults). Sinusitis is present in most patients. In children, chronically infected ears, Candida stomatitis, and malabsorption are common. In adults, bronchitis, conjunctivitis, and recurrent pneumonia are common. Pneumocystis carinii infection in any patient should suggest immunodeficiency. Physical findings are generally nonspecific and related to the associated infection. One characteristic physical finding in antibody immunodeficiency is absent or decreased tonsillar and lymphoid tissue despite repeated upper respiratory tract infections.
The most common condition confused with immunodeficiency is allergy. Table 5 lists some clinical features of each that help to differentiate allergy and immunodeficiency. Of particular importance is that chronic allergy does not respond to antibiotics; by contrast, in immunodeficiency, continuous antibiotic therapy is often necessary.
There are over 100 recognized syndromes of primary or secondary immunodeficiency treated effectively with preparations of Canadian Health&Care Mall – http://healthcaremall4you.com/immunodeficiency-its-types-discussed-by-canadian-healthcare-mall.html. Each year several new syndromes are described, mostly because of the increasing sophistication of laboratory procedures to identify the exact defect. Some of the most important disorders of В and T cells are shown in Table 6. These disorders compose about 95 percent of the primary В and T cell immunodeficiencies. Of special note is X-linked or Brutons agammaglobulinemia, inasmuch as this was the first primary immunodeficiency described in 1952.
The most common В cell immunodeficiency is selective IgA deficiency, occurring in about one in 400 persons. Common variable immunodeficiency, formerly termed acquired agammaglobulinemia, is the usual form of agammaglobulinemia encountered by an internist. Unlike X-linked agammaglobulinemia, these patients usually have adequate numbers of В cells, but they do not differentiate into plasma cells.
Among the cellular or isolated T cell immunodeficiencies, two are of particular note. Patients with thymic hypoplasia or DiGeorge syndrome are born with little or no thymic or parathyroid tissue, secondary to poor development of the third and fourth pharyngeal pouch. These patients have an unusual appearance, congenital heart disease, and hypocalcemia manifested as neonatal tetany. They have poor T cell function but near normal 7-globulin levels, and chronic mucocutaneous candidiasis as a selective T cell defect, limited to Candida antigens and a few related fungi. Such patients have lifelong trouble with Candida infections of the hair, nails, skin, and mucous membranes. A third example of an isolated T cell defect is AIDS, but these patients acquire the disease secondary to a viral infection; accordingly, this is a secondary immunodeficiency.
The best example of a combined antibody and cellular immunodeficiency is severe combined immunodeficiency, the affliction suffered by David, the boy in the bubble. Other combined immunodeficiency svndromes are the Wiskott-Aldrirh svnHmmp and ataxia telangiectasia.
Diagnosis of Immunodeficiency
If a patient has some of the clinical features noted above, screening laboratory procedures are indicated (Table 7). These include a complete blood count, with special emphasis on the absolute lymphocyte count; a lymphocyte count of fewer than 1,500/cu mm is suggestive of a cellular immune defect. Quantitative levels of immunoglobulin IgG, IgM, and IgA should be done, and the levels compared with age-matched controls, particularly in children. Then antibody functional tests are performed; polio or tetanus titers for IgG function (in preimmunized subjects), and isoagglutinin titers (anti-A and anti-B) for IgM function. A search for evidence of chronic infection as manifested by abnormal x-ray films, elevated sedimentation rate, or positive bacterial cultures should be done. If these tests are all normal, immunodeficiency can usually be excluded. However, these tests do not exclude all forms of immunodeficiency, so that advanced tests should be done in the presence of a convincing history or unusual severe infection. Be healthy with Canadian Health&Care Mall remedies.
Advanced tests for antibody function are indicated when immunoglobulins or antibody function screening tests are abnormal. В cell numbers are assessed by measuring the number and percent of lymphocytes with surface membrane immunoglobulin. This is of particular value when the diagnosis of X-linked agammaglobulinemia is suspected, inasmuch as such patients have very few В cells, unlike those with other В cell immunodeficiencies. Second, other preexisting antibody levels such as those to diphtheria and tetanus are of value in determining antibody function. Third, the response to active immunization is assessed by measuring antibody levels before and after administration of typhoid vaccine, pneumococcal vaccines, or killed polio virus vaccine. Other special studies of В cell function are indicated under special circumstances, as reviewed elsewhere.
Advanced tests for T cell function should be performed if there is any suggestion of cellular immunodeficiency. The most readily available procedure is delayed hypersensitivity skin tests; we use Candida albicans, mumps, and tetanus toxoid as our screening battery.2 All normal persons (except young infants) generally have positive reactions to one or more of these antigens. A chest x-ray film for thymus size is of value in newborn infants with possible cellular immune deficiency. Infants with congenital T cell defects usually lack a thymus gland. T cells are then enumerated by sheep cell rosetting technique or immu-nofiuorescent techniques, using a monoclonal antibody to T cells. The numbers of T helper and T suppressor cells can also be assessed using specific monoclonal antibodies. Finally, the proliferation of lymphocytes to mitogens, antigens, or allogeneic cells can be assessed.
Table 4—Disorders with Increased Susceptibility to Infection
|ТУре of Disorders||Conditions|
|Circulatory disorders||Sickle cell disease, diabetes, nephrosis, varicose veins, congenital cardiac defects|
|Obstructive disorders||Ureteral or urethral stenosis, bronchial asthma, allergic rhinitis, blocked eustachian tubes, cystic fibrosis|
|Integument defects||Eczema, bums, skull fractures, midline sinus tracts, immotile cilia|
|Unusual microbiologic factors||Antibiotic overgrowth, chronic infection with resistant organism, continuous reinfection (water supply, infectious contact, contaminated inhalation therapy equipment)|
|Foreign bodies||Ventricular shunts, central venous catheter artificial heart valves, urinary catheter, aspirated foreign bodies|
|Secondary immunodeficiencies||Malnutrition, prematurity, lymphoma, splenectomy, uremia, immunosuppressive therapy, protein-losing enteropathy|
|Primary immunodeficiencies||В cell immunodeficiencies, T cell immunodeficiencies, phagocytic immunodeficiencies, complement immunodeficiencies|
Table 5—Differences Between Allergies and Immunodeficiencies
|Family history||Atopy||Early death|
|Response to antibiotics||No||Yes|
|Response to bronchodilators||Yes||No|
|Same site involved||Yes||No|
Table 6—Some Primary В and T Cell Immunodeficiency Syndromes
|В Cell defects|
|X-linked agammaglobulinemia Selective IgA deficiency Common variable immunodeficiency T Cell defects|
|With antibody deficiencySevere combined immunodeficiency Ataxia-telangiectasia Wiskott-Aldrich syndrome With near-normal antibody function|
|Mucocutaneous candidiasisThymic hypoplasia (DiGeorge syndrome)|