ESSENTIALS OF DIAGNOSIS
Modes of transmission: sexual contact with an infected person, parenteral exposure to infected blood (transfusion or needle sharing), perinatal exposure.
Prominent systemic complaints: sweats, diarrhea, weight loss, and wasting.
Opportunistic infections due to diminished cellular immunity—often life-threatening.
Aggressive cancers, particularly non-Hodgkin lymphoma.
Neurologic manifestations, including dementia, aseptic meningitis, and neuropathy.
When AIDS was first recognized in the United States in 1981, cases were identified by finding severe opportunistic infections such as Pneumocystis pneumonia that indicated profound defects in cellular immunity in the absence of other causes of immunodeficiency. When HIV was identified as the cause of the syndrome, it became obvious that severe opportunistic infections and unusual neoplasms were at one end of a spectrum of disease, while healthy seropositive individuals were at the other end.
The earliest stage of HIV infection is acute infection. It is characterized by an illness with systemic symptoms including fever, rash, swollen lymph nodes, and aseptic meningitis. Diagnosis is made in a patient who was previously known to be HIV negative or of unknown HIV status in whom these characteristic symptoms develop following an exposure to HIV. If the HIV antibody tests are nonreactive, confirmation of the diagnosis is made by finding a positive HIV viral load (Table 31–2). If acute infection is suspected but the HIV viral load test is negative or if the viral load is positive but at a low level (< 1000 copies), the test should be repeated in 2 weeks. In patients with acute infection, antibodies will subsequently develop and immunoassays will become reactive. Patients with acute infection should receive prompt antiretroviral treatment (see Treatment section below).
Not all patients with HIV infection are diagnosed with acute illness. Patients may convert from being HIV-antibody negative to positive without having come to medical attention. Once the acute infection stage has passed, patients generally enter an asymptomatic phase; in the years prior to effective antiviral therapy, it was found that this asymptomatic stage could last for years, although during this time the immune system was being harmed.
The classification “AIDS” defines the late stage of HIV infection.
The Centers for Disease Control and Prevention (CDC) AIDS case definition (Table 31–1) includes opportunistic infections and malignancies that rarely occur in the absence of severe immunodeficiency (eg, Pneumocystis pneumonia, central nervous system lymphoma). It also classifies persons as having AIDS if they have positive HIV serology and certain infections and malignancies that can occur in immunocompetent hosts but that are more common among persons infected with HIV (pulmonary tuberculosis, invasive cervical cancer). Several nonspecific conditions, including dementia and wasting (documented weight loss)—in the presence of a positive HIV serology—are considered AIDS. The definition includes criteria for both definitive and presumptive diagnoses of certain infections and malignancies. Finally, persons with positive HIV serology who have ever had a CD4 lymphocyte count below 200 cells/mcL ...