Chapter 35 HIV Infection and AIDS
PATHOPHYSIOLOGY
Infection with the human immunodeficiency virus (HIV) occurs when the virus attaches to and enters helper T CD4 lymphocytes. The virus infects CD4 lymphocytes and other immunologic cells, and the person experiences a gradual destruction of CD4 cells. These cells, which amplify and replicate immunologic responses, are necessary to maintain immune function. When the CD+ lymphocytes are reduced in number, immune functioning begins to fail. As CD4+ lymphocytes decrease, the body is at risk for the development of opportunistic infections (OIs). When these CD4+ lymphocytes have decreased to fewer than 200 cells/mm3 (>15%), the client’s HIV infection has progressed to clinical acquired immunodeficiency syndrome (AIDS).
HIV can also infect macrophages, cells that permit HIV to cross the blood-brain barrier into the brain. B lymphocyte function is also affected, with increased total immunoglobulin production associated with decreased specific antibody production. As the immune system progressively deteriorates, the body becomes increasingly vulnerable to OIs and is also less able to slow the process of HIV replication. HIV infection is manifested as a multisystem disease that may be dormant for years as it produces gradual immunodeficiency. The rate of disease progression and clinical manifestations vary from person to person.
HIV is transmitted only through direct contact with blood or blood products and body fluids, such as cerebrospinal fluid, pleural fluid, human breast milk, semen, saliva, and cervical secretions. In the United States, intravenous drug use, sexual contact, perinatal transmission from mother to infant (also referred to as vertical transmission), and breast-feeding are established modes of transmission. There is no evidence that HIV infection is acquired through casual contact. Administration of zidovudine or nevirapine to pregnant HIV-infected women significantly reduces perinatal transmission.
Currently, the majority of reported cases of HIV infection and AIDS in the United States occurs in men who have sex with men (MSM). However, the highest rates of new HIV infections are among heterosexual individuals. With advances in the screening of blood products for HIV, the incidence of new infections from blood transfusions has been greatly reduced in developed countries.
Four populations in the pediatric age group have been primarily affected:
1. Infants infected through perinatal transmission from infected mothers; this accounts for more than 90% of AIDS cases among children younger than 13 years of age
2. Children who have received blood products from HIV-infected donors (especially children with hemophilia)
3. Adolescents infected after engaging in high-risk behavior
4. Infants who have been breast-fed by infected mothers (primarily in developing countries)
INCIDENCE
1. Children account for less than 2% of all reported cases of AIDS in the United States.
2. Over 90% of infected children in the United States acquired the infection from their mothers.
3. The number of infants infected by perinatal transmission has decreased significantly as a result of diagnosis and treatment of HIV-infected pregnant women.
4. AIDS is more prevalent in ethnic minority children. Currently, African-American, non-Hispanic children account for 62% of U.S. cases of AIDS, and Hispanic children account for 22%. White children comprise 15% of the total U.S. cases of AIDS.
CLINICAL MANIFESTATIONS
Infants and Children
The majority of children who are born to HIV-infected mothers become symptomatic during the first 6 months of life, with the development of lymphadenopathy as the initial finding (Box 35-1). The most common clinical manifestations include the following:
5. Recurrent upper respiratory tract infections
7. Chronic or recurrent diarrhea
8. Recurrent bacterial and viral infections
9. Persistent Epstein-Barr virus infection
Box 35-1 Clinical Categories of HIV Infection for Children Under 13 Years of Age
Category N: Not Symptomatic or One Condition Listed in Category A
Children with no signs or symptoms thought to be the result of HIV infection
Category B: Moderately Symptomatic
Children who have symptomatic conditions that are attributed to HIV infection:
• Anemia, neutropenia, thrombocytopenia persisting >30 days
• Bacterial meningitis, pneumonia, or sepsis
• Cytomegalovirus infection with onset before 1 month of age
• Diarrhea, recurrent or chronic
• Herpes stomatitis, recurrent
• Herpes simplex virus bronchitis, pneumonitis, or esophagitis with onset before 1 month of age
• Herpes zoster (shingles), two or more episodes
• Lymphoid interstitial pneumonia (LIP)
• Persistent fever lasting for over 1 month
• Thrush lasting longer than 2 months in a child >6 months
Category C: Severely Symptomatic (AIDS-defining conditions)
Children who have any of the following conditions:
• Bacterial infections, multiple or recurrent
• Candidiasis of the trachea, bronchi, lungs, or esophagus
• Chronic herpes simplex ulcer (>1 month duration) or bronchitis, pneumonitis, or esophagitis with onset after 1 month of age
• Coccidioidomycosis, disseminated or extrapulmonary
• Cryptococcosis, extrapulmonary
• Cryptosporidiosis with diarrhea lasting >1 month
• Cytomegalovirus disease (other than liver, spleen, nodes), onset after age 1 month
• Cytomegalovirus retinitis (with loss of vision)
