Acquired ImmunoDeficiency Syndrome

Disease class: HIV infections

Commonly known as 

• AIDS

 

Causes

• Chronic HIV infection without sufficient modern therapy.

 

Pathophysiology

Over time, HIV infection depletes the population of T lymphocytes in the body of a host. Once the immune dysfunction has reached a certain level of severity, minor infections become life-threatening and entirely new infections can occur. This state of severe immune dysfunction is known as AIDS. At that point, the immune system is unable to mount a response significant enough to prevent pathogenesis of organisms with poor virulence and infectivity.

 

Diagnosis

A diagnosis of AIDS is made when a patient has an accurate laboratory result of:

• a CD4+ T-cell count below 200 cells/µL
• a CD4+ T-cell percentage of total lymphocytes of less than 14%

The diagnosis is also made by the presence of AIDS-defining illnesses. These are diseases which only arise in patients with acquired immunodeficiency syndrome. This includes:

• Bacterial infections, multiple or recurrent*
• Candidiasis of bronchi, trachea, or lungs
• Candidiasis of esophagus^†
• Cervical cancer, invasive^§
• Coccidioidomycosis, disseminated or extrapulmonary
• Cryptococcosis, extrapulmonary
• Cryptosporidiosis, chronic intestinal (>1 month's duration)
• Cytomegalovirus disease (other than liver, spleen, or nodes), onset at age >1 month
• Cytomegalovirus retinitis (with loss of vision)^†
• Encephalopathy, HIV related
• Herpes simplex: chronic ulcers (>1 month's duration) or bronchitis, pneumonitis, or esophagitis (onset at age >1 month)
• Histoplasmosis, disseminated or extrapulmonary
• Isosporiasis, chronic intestinal (>1 month's duration)
• Kaposi sarcoma^†
• Lymphoid interstitial pneumonia or pulmonary lymphoid hyperplasia complex*^†
• Lymphoma, Burkitt (or equivalent term)
• Lymphoma, immunoblastic (or equivalent term)
• Lymphoma, primary, of brain
• Mycobacterium avium complex or Mycobacterium kansasii, disseminated or extrapulmonary^†
• Mycobacterium tuberculosis of any site, pulmonary,^†§ disseminated,^† or extrapulmonary^†
• Mycobacterium, other species or unidentified species, disseminated^† or extrapulmonary^†
• Pneumocystis jirovecii pneumonia^†
• Pneumonia, recurrent^†§
• Progressive multifocal leukoencephalopathy
• Salmonella septicemia, recurrent
• Toxoplasmosis of brain, onset at age >1 month^†
• Wasting syndrome attributed to HIV

* Only among children aged <13 years. (CDC. 1994 Revised classification system for human immunodeficiency virus infection in children less than 13 years of age. MMWR 1994;43[No. RR-12].)
^† Condition that might be diagnosed presumptively.
^§ Only among adults and adolescents aged >13 years. (CDC. 1993 Revised classification system for HIV infection and expanded surveillance case definition for AIDS among adolescents and adults. MMWR 1992;41[No. RR-17].)