Parasitic diseases in immunocompromised hosts.

In patients with compromised host defenses, diseases caused by protozoans and nematodes appeared, a few years ago, to be declining in importance. However, the outbreak of the acquired immunodeficiency syndrome (AIDS) among homosexual men, parenteral drug abusers, and other groups has made it necessary for physicians to familiarize themselves again with the manifestations of these diseases in abnormal hosts. The groups of patients at greatest risk, the usual clinical syndromes in abnormal hosts, and current approaches to diagnosis, treatment, and prevention of infections due to Pneumocystis carinii, Toxoplasma gondii, Strongyloides stercoralis, and organisms of the genus Cryptosporidium are reviewed. Because so many cases of these infections have recently occurred among patients with AIDS, recent experience with these diseases in AIDS patients at Memorial Sloan-Kettering Cancer Center is summarized.