Opportunistic Infections

Basics

Description

Unusual infections that occur when host suffers a decrease in resistance against normally nonpathogenic organisms

Etiology

  • Occurs in HIV patients when the CD4 T-lymphocyte count falls below 200 cells/mm3 or <14% of the total lymphocyte count:
    • Pneumocystis jirovecii pneumonia (PCP)
    • Disseminated tuberculosis
    • Cryptosporidiosis
    • Microsporidiosis
    • Isosporiasis
    • Toxoplasmosis
    • Histoplasmosis
    • Cryptococcosis
    • Mycobacterium avium complex
    • Tuberculosis pericarditis or meningitis
    • Cytomegalovirus
    • Human herpesvirus-8 (Kaposi sarcoma)
    • JC virus (progressive multifocal leukoencephalopathy)
    • Hepatitis B virus
    • Penicilliosis marneffei
    • Bacterial species
  • Cell-mediated deficiency:
    • Hematologic malignancies
    • Lymphoma
    • High-dose glucocorticoid therapy
    • Autoimmune disorders
    • Viral infections
    • Cytotoxic drugs/chemotherapy
    • Radiation therapy
    • Associated with:
      • Legionella
      • Nocardia
      • Salmonella
      • Mycobacteria
  • Neutrophil impairment/depletion:
    • Cytotoxic drugs
    • Aplastic anemia
    • Drug reactions:
      • Dapsone
    • Neoplastic invasion of bone marrow
    • Arsenic
    • Penicillin
    • Chloramphenicol
    • Procainamide
    • Vitamin deficiencies
    • Associated with:
      • Staphylococcus and α-hemolytic Streptococcus
      • Enteric organisms and anaerobes
      • Invasive aspergillosis
  • Immunomodulatory drugs:
    • TNF-α inhibitors
      • Inflixamab > etanercept
      • Rituximab
      • Adalimumab
    • Azathioprine
  • Consider hepatitis, Herpes zoster and M. tuberculosis reactivation

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