AIDS-defining conditions


CD4+ cell count < 500/mm3

CD4+ cell count < 200/mm3

CD4+ cell count < 100/mm3

  • Cerebral toxoplasmosis
  • Extrapulmonary cryptococcosis (especially cryptococcal meningitis)
  • Cryptosporidiosis
    • Etiology: Cryptosporidium species
    • Clinical features: chronic, watery diarrhea (lasting > 1 month) with nausea and abdominal pains; typically at CD4 counts < 100
    • Diagnostics: acid-fast oocysts in stool
  • Esophageal candidiasis or pulmonary candidiasis
    • Oropharyngeal candida, which is not AIDS-defining, is more common as CD4 counts decline, and may be seen when CD4 count is < 200–250.
    • Neutrophils are the most important immune cell in the defense against invasive Candida infection; therefore, patients with neutropenia (eg, following cytotoxic chemotherapy) are at high risk for invasive disease (eg, candidemia, meningitis). In contrast, T lymphocytes are more important for prevention of superficial, mucocutaneous infection (eg, thrush).
  • Primary CNS lymphoma
  • Disseminated and/or extrapulmonary Mycobacterium avium complex
  • Cytomegalovirus infection

CD4+ cell count < 50/mm3

  • Disseminated and/or extrapulmonary Mycobacterium avium complex
  • Cytomegalovirus infection
  • Aspergillosis

Neurological complications


HIV-associated neurocognitive disorder (HAND)

  • Definition: neurocognitive impairment in patients with HIV that cannot be attributed to a cause other than HIV infection. HAND is typically a diagnosis of exclusion.
  • Etiology: thought to result from a combination of dissemination of HIV into the CNS and the resultant immune activation.
  • Epidemiology: common even in patients with well-controlled HIV (affecting up to 50% of individuals)
  • Clinical features
    • Early: mild impairment in attention, recall, and executive function
    • Advanced: HIV-associated dementia (considered an AIDS-defining condition)
      • Subcortical dementia: memory loss, depression, movement disorders, behavioral changes (e.g., apathy)
      • Severe neurologic deficits: altered mental state, aphasia, gait disturbances
      • More common in patients with advanced or untreated HIV
  • Diagnostics
    • Imaging: CT or MRI brain without and with IV contrast
      • Diffuse cerebral atrophy; disproportionate to the patient’s age
      • Patchy symmetrical changes in the periventricular and deep white matter
      • No mass effect, no contrast-enhancement
    • Histopathology shows giant cells with multiple nuclei (formed through fusion of HIV-infected monocytes).