Pneumocystis jirovecii Pneumonia in Human Immunodeficiency Virus Infection.

The presentation of Pneumocystis pneumonia (PCP) in previously healthy men having sex with men (MSM) in San Francisco and New York City in 1981 heralded the beginning of the human immunodeficiency virus (HIV) pandemic. Despite a decreasing incidence of PCP among patients with HIV/AIDS (acquired immunodeficiency syndrome) since the advent of combination antiretroviral therapy in the mid-1990s, PCP remains one of the most common AIDS-defining opportunistic infections in the United States and Western Europe. Newer molecular diagnostic tests in conjunction with standard immunofluorescent or colorimetric tests have allowed for more rapid and accurate diagnosis. Although several effective oral and intravenous therapies exist to treat PCP, mortality rates in HIV-infected individuals remain unacceptably high, especially in those with advanced AIDS. The identification of specific mutations in Pneumocystis genes targeted by trimethoprim-sulfamethoxazole has raised concerns about the development of resistance to the drug of choice and may ultimately lead to greater utilization of alternative therapies to treat PCP in the future.