Toxoplasmosis in the compromised host.

In 81 cases of toxoplasmosis in patients with neoplasia, collagen-vascular disorders, and organ allografts, the clinical manifestations were highly variable but neurologic syndromes consistent with diffuse encephalopathy, meningoencephalitis, or cerebral mass lesions predominated. Many concomitant infections with DNA viruses were seen. The diagnosis of toxoplasmosis was not made until postmortem examination in most cases. Biopsy of lymph nodes or brain and serologic tests needed for definitive diagnosis were done infrequently. Twenty patients received antitoxoplasma chemotherapy (pyrimethamine and sulfonamide), 16 (80%) showing marked clinical improvement or complete remission. In immunosuppressed hosts disseminated toxoplasmosis appears to result from defects in cellular immunity that permit recrudescence of latent infection. Because cell-mediated immunity to Toxoplasma gondii can be enhanced in animals by administration of adjuvants, immunotherapy may become a useful adjunct to chemotherapy in immunoincompetent humans suffering potentially lethal infection.