Orderly Function of the Immune System

The immune system, a major defense mechanism, is responsible for a complex response to the invasion of the body by foreign substances. The concept of the immune system arose from an observation that a person who recovers from a specific infection does not get sick from that infection again. The person is thereafter “immune” to that particular infectious agent. Immunity is very specific in that a person who has developed immunity to a certain virus, such as the rubella virus, is still susceptible to infection by different viruses, such as the measles virus.

The immune response assists the body in maintaining its functional integrity, and it battles infection by bacteria, viruses, fungi, and parasites. The immune system involves lymphoid tissues classified as primary (thymus and bone marrow) or secondary (tonsils, adenoids, spleen, Peyer’s patches, appendix, etc.) (Figure 3-1).

When the immune system reacts appropriately to an antigen and homeostasis is maintained, a person is immunocompetent. If the immune system’s response is inappropriate, either too weak or too strong, it results in the disruption of homeostasis. This malfunction in the system is referred to as immunoincompetence. Disruption of homeostasis is the cause of many diseases. Inappropriate responses or malfunctioning of the immune system are classified as follows:

The immune response normally is activated whenever foreign substances, or antigens, enter the body by evading its first line of defense—the skin and mucous membranes. The body recognizes the antigen or immunogen, usually a protein, as foreign, or non-self, and produces antibodies in response to that specific antigen. It is crucial that the immune system be able to differentiate between self and foreign molecules. When this is not the case, autoimmune disease is the result. In autoimmune disease, the body mistakenly recognizes molecules of its own tissues as foreign and then attacks them.

 Enrichment

Transplant Rejection

Kidney, liver, heart, lung, pancreas, intestines, and corneal tissue all can be replaced with transplants. Skin transplants are used for the treatment of burns. Bone marrow transplantation is used to treat many conditions such as bone marrow failure, leukemia, and aplastic anemia. E3-1

To help prevent transplant rejection, donor and recipient are carefully matched for blood type and immunologic characteristics. The recipient is given antirejection (immunosuppressive) drugs and steroids to suppress the production of antibodies to the foreign tissue proteins. All homografts (a graft of tissue between two genetically dissimilar individuals of the same species) invariably evoke some transplant rejection, which is mediated by antibodies and a delayed cellular immune reaction.

Clinically distinct forms of transplant rejection are recognized:

• Hyperacute reaction occurs during the operation. The transplanted organ must be removed immediately to prevent inevitable complications.

• Acute rejection occurs most often within the first few weeks of transplantation, or later when antirejection drugs become ineffectual.

• Chronic rejection evolves slowly over a period of months or years. Vascular injury and inflammation of the tissues and cells of the organ contribute to the ultimate deterioration of the transplanted organ.

Modified from Damjanov I: Pathology for the health-related professions, ed 3, Philadelphia, 2005, Saunders.

The mechanisms of nonspecific defense involve preformed and fully activated components that launch a nonspecific attack on a foreign organism as soon as it is detected. The main cells involved in nonspecific defense include the following:

The development of the components required for immunity begins early in fetal life when the fetal liver produces stem cells, which in turn produce all cells of the hematopoietic system. Bone marrow assumes this role after birth (Figure 3-3). Some of the stem cells migrate to the thymus gland, where they become T cells (T lymphocytes), which multiply and develop the capacity to combine with specific foreign antigens derived from viruses, fungi, tumors, or transplanted tissue (Figure 3-4). Those T cells coded to recognize self-antigens are destroyed. The remaining T cells are coded to seek out foreign invaders. The body produces several types of T cells; each has a different function:

T cells are the major component of the type of acquired immunity known as cell-mediated immunity. The mononuclear phagocytic system, formerly termed the reticuloendothelial system, initiates this immune response. Macrophages, which develop from monocytes, are found in the tissue of the liver, lungs, and lymph nodes. These large cells intercept and engulf the foreign invader antigens, then process and present them to the T cells. Cell-mediated immunity defends the body against viral and fungal attacks, mediates graft rejection and tumor cell destruction, and helps or suppresses an antibody-mediated response to infection.

The remaining stem cells develop into B cells (B lymphocytes) to produce the antibody-mediated (humoral) immunity that protects the body against bacterial and viral infections and reinfections (see Figure 3-4). Once activated by exposure to an antigen, B cells are stimulated to proliferate and form a clone of cells that respond to that specific antigen. Some B cells become antibody-secreting plasma cells, whereas others become memory B cells, ready for a quick response if the target antigen presents itself again. The plasma cells are responsible for producing antibodies that attach to invading foreign antigens, thus marking the antigens for destruction by other cells of the immune system.

B cells are coated with immunoglobulins, giving them the ability to recognize foreign protein and stimulate an antigen-antibody reaction. The five classes of immunoglobulins or antibodies are IgM, IgG, IgA, IgD, and IgE (Table 3-1). These immunoglobulins are usually all present during an antigenic response, although in varying amounts, depending on the stimulant and the health of the patient. Actions of the antigen-antibody complex include the following:

Activation of the complement system (complement fixation) involves several proteins found in plasma or body fluids. The antigen-antibody reaction initiates a series or cascade of reactions that activate the complement system, fixing the complement and consequently permitting the destruction of pathogens by the process of phagocytosis or lysis of the pathogen’s cell membrane. This activation occurs during an immune reaction mediated by IgG or IgM.

The human body is protected by two types of acquired specific immunity: active immunity and passive immunity. Active immunity results when a person has had previous exposure to a disease or pathogen, or when a person receives immunizations against a disease to stimulate the production of a specific antibody. Active immunity affords the person acquired permanent protection. Passive immunity bypasses the body’s immune response to afford the benefit of immediate antibody availability. A person gains passive immunity by being given immune substances created outside that person’s body for temporary immunity, such as antibodies received through the placenta, when breast milk is fed to a child, or when immune globulin, an antibody-containing preparation made from the plasma of healthy donors, is given to help a person combat disease (Figure 3-5).

Immunodeficiency Diseases

An absent or inadequate response of the immune system results in immunodeficiency conditions and increased susceptibility to other diseases and opportunistic infections. Immunodeficiency can occur in any of the following major components of the immune system: B cells, T cells, complement, or phagocytes. Although the deficiency may be in either the humoral (antibody-related) or the cell-mediated responses, the consequences are similar: the individual does not have the capability to dispose of foreign and harmful substances. In general, an increased susceptibility to bacterial infections results from a B-cell deficiency, whereas recurrent viral, fungal, and protozoan infections are usually due to decreased T-cell function. Some of the conditions are genetic and present at birth, whereas other defects are not manifested until later in life or are acquired. Acquired immunoincompetence may result from a bacterial or viral insult to the body, malnutrition, or exposure to radiation or certain drugs. The severity of the immunodeficiency disease depends on the type of cell or cells that are affected. It can range from annoying chronic infections to severe life-threatening or fatal conditions. E3-2

 Enrichment

Malignancies and Common Opportunistic Infections and Conditions in Patients With AIDS

• Kaposi sarcoma is an aggressive malignancy of the blood vessels that appears as purple or blue patches on the skin, in the mouth, or anywhere else on the body

• Lymphomas are cancerous lesions of lymphoid tissues.

• Pneumocystis carinii pneumonia (PCP) is a lung infection that can progress to be life threatening. It is the most common lung disease in persons with AIDS.

• Tuberculosis is a bacterial infection of the lungs or other organs.

• Herpes simplex consists of painful blisterlike lesions of the mouth, genitalia, or anus caused by the herpes virus

• Herpes zoster (shingles) is characterized by clusters of red blisterlike skin lesions that follow an inflamed nerve path.

• Candida albicans causes a fungal infection of the mucous membranes of the mouth, genitalia, or skin.

• Toxoplasmosis is an infection caused by a protozoan intracellular parasite. A rash and lymphadenopathy can be present, and the central nervous system, heart, or lungs can become involved.

• Neurologic complications include inflammation of nerves, neuropathy, neoplasms, and AIDS dementia complex.

• Diarrhea is a symptom of a host of bacterial and viral infections of the gastrointestinal tract, liver, or gallbladder.

• Epstein-Barr virus causes hairy leukoplakia that is characterized by white plaque visible on the tongue.

Acquired Immunodeficiency Syndrome (AIDS)

Description

Acquired immunodeficiency syndrome (AIDS) is a progressive impairment of the immune system caused by the human immunodeficiency virus (HIV). This gradual destruction of the immune system affects many organ systems and is ultimately lifethreatening for the person infected.

 ICD-9-CM Code 042

 ICD-10-CM Code B20 (Human immunodeficiency virus (HIV) disease)

Symptoms and Signs

Initially it is not possible to tell whether people are infected with HIV by simply observing them. They may remain healthy for years during the latent period and may therefore unknowingly transmit the virus to other people. Within 1 to 4 weeks after exposure, the patient may experience a flulike illness with sore throat, fever, and body aches that often lasts about 2 weeks. Lymphadenopathy, weight loss, fatigue, diarrhea, and night sweats are common as the clinical course progresses. The body’s number of T cells becomes lower and allows for frequent infections, especially opportunistic infections, pneumonia, fever, and malignancies (see the Enrichment box for Malignancies and Common Opportunistic Infections and Conditions in Patients with AIDS). Often, in the later stages, encephalopathy and malignancy lead to dementia and death (Figure 3-9).

Patient Screening

An individual who complains of weight loss, fatigue, swollen glands, night sweats, and/or a persistent flulike syndrome needs an appointment with a physician for a medical evaluation as soon as possible. When an individual reports a known HIV exposure through unprotected sexual contact or puncture with a contaminated needle, immediate medical care should be arranged.

Etiology

AIDS is caused by HIV, type 1 or 2 (HIV-1 is found worldwide, HIV-2 is mainly in West Africa) retroviruses that contain RNA; they cannot survive apart from human cells. HIV attacks helper T lymphocytes (CD4 cells), the body’s safeguard against tumors, viruses, and parasites. The destruction of T cells and the proliferation of HIV leave the body defenseless against infection and malignancy by reducing cell-mediated immunity. The virus also directly damages the nervous system. AIDS first was recognized in the United States in 1981. Since then, it has become a top killer of young men and a worldwide threat to humankind. It is estimated that close to 35 million people are currently infected with the AIDS virus and more than 30 million have already died from the illness. Without treatment, the time from infection with HIV to death is approximately 10 years. To date, neither a cure nor an effective vaccine has been found for this disease, although use of highly active antiretroviral therapy (HAART) has significantly prolonged the life span of those infected.

HIV is spread most readily by direct contact with the blood or semen of an infected person. It is not transmitted by casual contact, such as touching, handshaking, and hugging. Sexual contact is the primary means of transmission. Although AIDS initially was associated with homosexual activity, now most people are infected through heterosexual transmission. AIDS also can be transmitted through blood and blood products. Infants of infected mothers can contract the disease in utero through the placenta, during the birth process, and from breast milk. Sharing of needles by intravenous drug users also leads to infection. The risk of transmission of HIV to and from health care workers and patients is minimized by strict adherence to the universal precautions for infection control.

Diagnosis

A common laboratory screening test used to detect the presence of HIV antibodies in the blood is the enzyme-linked immunosorbent assay (ELISA). If the findings are positive, the test is repeated, and the result is then confirmed by using a Western blot test. A positive p24 antigen test indicates circulating HIV antigen. ELISA tests are often negative during the first month of infection, although a p24 antigen test or polymerase chain reaction (PCR) assay may be positive. Rapid HIV antibody testing has become the preferred method of testing as the results are often available within 5 minutes. Although a negative test is regarded as a true negative, a positive result requires confirmatory testing by Western blot. A viral titer and CD4 T-cell count are usually obtained following a positive test to determine the patient’s disease burden and risk for opportunistic infections. Transmission of HIV is possible during all stages of infection, even before it can be detected by laboratory tests.

Treatment

Currently, no cure exists for AIDS. After a patient has been diagnosed, he or she will have periodic measurement of the number of CD4 T cells and the amount of HIV RNA (viral load) present in the bloodstream. These are both markers of disease progression from the initial infection with HIV to the development of AIDS. These numbers can also be used to determine when to begin HAART. HAART consists of a three drug combination: two nucleoside reductase inhibitors and either a nonnucleoside reductase inhibitor or a protease inhibitor. There are currently 20 antiretroviral drugs approved for use in HAART, so many different drug combinations are possible. Although these drugs have been effective at prolonging life and maintaining the quality of life for patients, they are associated with a number of toxicities and serious side effects so patients on HAART must be followed closely. In the later stages of the disease, patients will require prophylactic antibiotics. Addressing the psychological needs of the patient with AIDS is essential.

Health care practitioners who are involved in various forms of patient care with exposure to body fluids and blood should follow the principles of infection control and universal precautions (see the Alert box for Infection Control and Universal Precautions). All body fluids and blood from any patient should be handled with extreme care, as if the patient were known to be infected with HIV.

Prognosis

Although AIDS is ultimately a fatal disease, the number of Americans dying of AIDS each year has dropped. Treatment strategies that result in better prognosis include use of HAART, use of prophylactic antibiotics, and care by a physician experienced with HIV care.

Prevention

Because HIV is transmitted directly from human to human, prevention measures relate to avoiding risk factors for sexually transmitted diseases and practicing infection control through the use of universal precautions. Use of condoms and not sharing needles are highly recommended. The drugs used in highly active antiretroviral therapy (HAART) can be administered as postexposure prophylaxis after a needlestick injury.

Patient Teaching

Describe the diagnostic tests and inform the patient concerning when to expect test results. Assure the patient of medical confidentiality. Make sure the HIV-positive individual knows how the disease is transmitted. Stress important aspects of the medication regimen and the dangers of noncompliance. Explain side effects of the therapeutic drugs, and encourage him or her to contact the health care worker with questions or concerns. Other teaching points will include how to minimize infections, the need for lifelong therapies, and the responsibility to inform health care providers about the HIV diagnosis. The psychological, social, and financial ramifications of having HIV require referrals for community support. Eventually, referrals will be required to meet a variety of home care needs.

 Alert

Infection Control and Universal Precautions

Guidelines: Treat blood and body fluids as if infected and remember to use the following precautions:

1. Practice frequent and thorough hand washing.

2. Report any accidental needlesticks.

3. Wear personal protective equipment, including mask or face shield, gown, gloves, and goggles. Change equipment between patients.

4. Use caution with laboratory specimens.

5. Dispose of contaminated sharps in designated biohazard containers. Caution: Do not recap or break needles.

6. Use proper linen disposal containers.

7. Use clean mouthpieces and resuscitation bags.

8. Obtain hepatitis B vaccination to protect against occupational exposure to blood.

9. Use proper decontamination techniques.

10. Absorb blood spills with paper towels, then clean the area with soap and water, followed by disinfection of the area with a 1 : 10 solution of household bleach. E3-3

NOTE: Pathogens can be bloodborne or airborne. Standard Precautions, which correlate with Universal Precautions, are recommended and posted for hospitals and patient care institutions.

Common Variable Immunodeficiency (Acquired Hypogammaglobulinemia)

Description

Common variable immunodeficiency (CVID) is an acquired B-cell deficiency that results in decreased antibody production and/or function.

 ICD-9-CM Code 279.06

 ICD-10-CM Code D83.8 (Other common variable immunodeficiencies)

D83.9 (Common variable immunodeficiency, unspecified)

(D83.0-D83.9 = 5 codes of specificity)

Symptoms and Signs

The person with CVID has a history of chronic or recurrent infections, such as pneumonia, bronchitis, sinusitis, and otitis media. Gastrointestinal disease is common with symptoms including diarrhea, abdominal pain, and weight loss. Lymphadenopathy, splenomegaly, and hepatomegaly often are observed. CVID is associated with an increased frequency of autoimmune disorders such as autoimmune hemolytic anemia. As the disease progresses and T-cell involvement occurs, susceptibility to opportunistic and viral infections and malignancies escalates.

Patient Screening

When a child or young teenager is susceptible to frequent infection, it is recommended that an appointment to discuss options be made with the health care provider or that office policy regarding referral to a pediatrician be followed. When the individual, particularly a younger adult, experiences frequent bacterial infections, an appointment for an in-depth medical investigation is indicated.

Etiology

CVID has two peaks of incidence: one between the ages of 18 and 25 years, and a smaller peak from ages 1 to 5 years. Although the exact cause of hypogammaglobulinemia is not known, it is thought to be a result of genetic defects leading to immune system dysregulation and a failure of B-cell differentiation. The number of circulating B cells is often normal, but the ability of the B cells to produce all types of immunoglobulins is reduced. Some patients have impaired T-cell signaling as well. Cell-mediated immunity usually remains intact.

Diagnosis

A history of repeated and chronic infections should lead to further investigation of immunoglobulin levels and T-cell quantities. Antibody response to vaccines, when tested, is poor. Hypogammaglobulinemia and IgA and/or IgM deficiency in this clinical setting are indicative of the disease.

Treatment

Treatment is aimed at preventing infections and implementing early treatment with appropriate antibiotic administration when infections occur. Regular immunoglobulin replacement decreases the number of infections, antibiotic usage, and hospitalizations. Proper nutrition and adequate rest are encouraged. Patients should be monitored closely because they are at an increased risk for development of autoimmune disease and lymphoma. Live virus vaccines are often not given to people known to have CVID, but no adverse events have been reported.

Prognosis

Although the use of immunoglobulin has improved the prognosis, patients often succumb to chronic lung disease or malignancies. Lower levels of immunoglobulin and a lower percentage of B cells are associated with a poorer prognosis.

Prevention

No methods of prevention are known.

Patient Teaching

Teaching points include steps to take to prevent infection and to ensure good nutrition, adequate rest, and regular follow-up care.

Selective Immunoglobulin A Deficiency

Description

Patients with selective immunoglobulin A (IgA) deficiency fail to produce the normal levels of IgA. Selective deficiencies of IgM or IgG have been reported but are rare.

 ICD-9-CM Code 279.01

 ICD-10-CM Code D80.2 (Selective deficiency of immunoglobulin A (IgA))

(D80.0-D80.9 = 10 codes of specificity)

Symptoms and Signs

The majority of patients with IgA deficiency are asymptomatic, perhaps because of a compensatory increase in IgM production in these patients. Those who do experience symptoms have recurrent sinopulmonary infections, gastrointestinal infections, and concurrent autoimmune disease. Food allergies are also common. Anaphylactic reactions to blood transfusions may occur. Children with selective IgA deficiency typically exhibit recurrent otitis media and respiratory tract disease.

Patient Screening

Frequent recurrent infections in a child or adult necessitate an appointment for a medical investigation to determine a possible underlying cause. The patient may also report food allergies and a history of an anaphylactic reaction to blood transfusions.

Etiology

Failure to produce adequate levels of IgA is the most common immunologic defect in the general population. Autosomal dominant or recessive inheritance appears to play a role in the etiology of this condition, in which B cells are not secreting IgA. It is thought that some patients with the disease will progress to common variable immunodeficiency (CVID).

Diagnosis

In patients over the age of 6 months with recurrent sinopulmonary infections, IgA deficiency should be considered. Levels of immunoglobulins should be measured and should show below-normal levels of circulating IgA, but normal IgG and IgM levels. Other immunoglobulin levels are normal. As some children with IgA deficiency may spontaneously begin to produce IgA, the diagnosis is not definite until after age 4.

Treatment

No cure for this condition is known, although some patients may spontaneously begin to produce IgA. Treatment is geared toward the prevention and management of infection. Prophylactic antibiotics may be given. If these do not reduce the number of infections, intravenous immune globulin (IVIG) with low concentrations of IgA may be tried. Patients should be monitored for development of autoimmune disease and progression to CVID. Patients must be monitored closely when given blood products because of the increased risk of an anaphylactic reaction.

Prognosis

In most cases, no significant medical problems are expected and the prognosis is good. Some children may show a slow, spontaneous resolution of the condition.

Prevention

No method of prevention is known.

Patient Teaching

Teaching points include steps to take to prevent infection and to ensure good nutrition, adequate rest, and regular follow-up care. Explain the purpose of prophylactic antibiotic therapy, as prescribed.

X-Linked Agammaglobulinemia

Description

X-linked agammaglobulinemia (Bruton’s agammaglobulinemia) is a condition characterized by near absence of serum immunoglobulins and increased susceptibility to infection.

 ICD-9-CM Code 279.04

 ICD-10-CM Code D80.0 (Hereditary hypogammaglobulinemia)

Symptoms and Signs

The infant with X-linked agammaglobulinemia has absent or near absent tonsils and adenoids. Lymphadenopathy and splenomegaly are also noticeably missing. They are susceptible to recurrent severe gram-positive infections, including bacterial otitis media, bronchitis, pneumonia, osteomyelitis, and meningitis. These are usually first noted between 3 and 18 months of age, when the natural transplacental immunity from the mother has been depleted.

Patient Screening

Recurrent severe bacterial infections in an infant signal the need for in-depth medical investigation to determine the possible underlying cause(s). Follow office policy for referral to a pediatrician when appropriate.

Etiology

This congenital X-linked disorder affects only males. It is due to a defect in the Bruton tyrosine kinase (BTK) gene, which is normally expressed in B cells during all stages of development. All five immunoglobulin classes are usually absent, along with the absence of circulating B cells and the presence of normal numbers of circulating T cells. This leads to increased infection with encapsulated bacteria and certain viruses. Most affected individuals present with symptoms by 5 years of age.

Diagnosis

The clinical findings, along with a thorough history including family history of relatives who died of severe infections, will suggest X-linked agammaglobulinemia. Immunoelectrophoresis indicates decreased levels of serum IgM, IgA, and IgG; however, relying on this method of diagnosis is not valid before the infant is 6 to 8 months of age. Serum antibody titers in response to immunizations are low. Other findings suggestive of this disease are normal T-cell numbers along with low or absent B-cell numbers. It may be useful to measure the amount of BTK by Western blot if there is no significant family history to aid diagnosis.

Treatment

Treatment is directed at improving the child’s immune defenses and controlling infections. Intravenous infusions or subcutaneous administrations of immune globulin every 2 to 4 weeks and appropriate antibiotics are administered. These patients must never be immunized with live virus vaccines, nor should corticosteroids or immunosuppressive drugs be administered.

Prognosis

Although this condition cannot be cured, regular infusions of immune globulin may provide the patient with an almost normal lifestyle. Affected individuals do miss more days of school or work and are hospitalized more frequently than males in the general population, however.

Prevention

No methods of prevention are known, although parents of affected children are encouraged to seek genetic counseling regarding future pregnancies.

Patient Teaching

Discuss the importance of preventing infections. Explain the procedure for immune globulin administrations. Caution the parents about the contraindication for live virus vaccines and immunosuppressive drugs.

Severe Combined Immunodeficiency

Description

Severe combined immunodeficiency (SCID) is a group of disorders that result from a disturbance in the development and function of both T cells and B cells. This leads to an absence of both cell-mediated (T-cell) and antibody-mediated (B-cell) immunity.

 ICD-9-CM Code 279.2

 ICD-10-CM Code D81.0 (Severe combined immunodeficiency (SCID) with reti-cular dysgenesis)

D81.1 (Severe combined immunodeficiency (SCID) with low T- and B-cell numbers)

D81.2 (Severe combined immunodeficiency (SCID) with low or normal B-cell numbers)

D81.89 (Other combined immunodeficiencies)

D81.9 (Combined immunodeficiencies, unspecified)

(D81.0-D81.9 = 13 codes of specificity)

Symptoms and Signs

SCID manifests as severe, recurrent infections with bacteria, viruses, fungi, and protozoa; chronic diarrhea; and failure to thrive. This occurs by the age of 3 to 6 months, when the natural maternal placental immunity begins to deplete. Common infections are Pneumocystis pneumonia and mucocutaneous candidiasis. Discernible lymphoid tissue (enlarged tonsils, palpable lymph nodes, etc.) may be absent. Abnormal laboratory findings often include hypogammaglobulinemia and very low or absent T cells.

Patient Screening

Abnormal newborn screen results must be followed up. The history of pneumonia in the first weeks of life, followed by frequent, severe infections in the young infant are indicative of underlying conditions that need a complete medical evaluation. These infections are potentially life threatening in the infant and immediate medical care is required. Follow office policy for referral to a pediatrician.

Etiology

Two types of SCID are known: X-linked and autosomal recessive. Both are due to different genetic mutations that lead to defects in stem cell differentiation into B cells and T cells. These defects result in a disruption in lymphocyte development.

Diagnosis

Testing for SCID is now part of the routine newborn screen in the United States. If the clinical picture indicates suspicion of SCID, many laboratory tests are performed. These include measurement of immunoglobulin levels, antibody titers, and numbers of T cells and B cells. Lymphopenia, with less than 20% of lymphocytes being T cells, is a common finding. T-cell response is also tested. There is usually absence of the thymic shadow on a chest radiograph.

Treatment

Bone marrow transplantation is the only curative treatment for most types of SCID, although gene therapy is being investigated. Preventing exposure to infection and assisting the immune response through bone marrow transplantation are the goals of treatment. Supportive therapy includes intravenous immune serum globulin. Children with SCID are placed in completely sterile environments to prevent exposure to infectious agents. Live vaccines should not be administered.

Prognosis

Unless the underlying gene defect is corrected, these children will die of overwhelming infection before the age of 1 year.

Prevention

No methods of prevention are known, although routine newborn screening aids in a timely diagnosis.

Patient Teaching

Explain the medical interventions used to protect against infection and restore immune response. Refer parents to available community support organizations that can help with the psychological, physical, and financial burdens precipitated by the infant’s prognosis of severe illness and early death. During hospitalizations, encourage the parents to visit and interact with the infant as much as possible. Refer the parents to a genetic counselor.

DiGeorge’s Anomaly (Thymic Hypoplasia or Aplasia)

Description

DiGeorge’s anomaly is a congenital condition of immunodeficiency that results from defective development of the pharyngeal pouch system and presents with cardiac anomalies, hypoplastic thymus, and hypocalcemia. In some coding manuals, this disease may be listed as DiGeorge’s syndrome.

 ICD-9-CM Code 279.11

 ICD-10-CM Code D82.1 (DiGeorge’s syndrome)

(D82.0-D82.9 = 7 codes of specificity)

Symptoms and Signs

Children with DiGeorge’s anomaly often have a set of structural abnormalities. These include abnormally wide-set, downward slanting eyes; low-set ears with notched pinnas; a small mouth (Figure 3-10); abnormalities of the palate; and cardiovascular defects such as tetralogy of Fallot. The thymus and parathyroid glands are absent or underdeveloped. The infant exhibits signs of tetany due to hypocalcemia caused by hypoparathyroidism. Some degree of cognitive impairment often is present. The patient is susceptible to severe viral, fungal, and protozoan infections. The most common of these are pneumonia and thrush in infants.

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