Toxoplasmosis: a treatable neurologic disease in the immunologically compromised patient.

A 10-year-old girl with aplastic anemia developed seizures and a mild hemiparesis following a bone marrow transplant. Based on serologic evidence and a computed tomography scan, which showed a left parietal lucency with ring enhancement, a diagnosis of toxoplasmosis was considered. A brain biopsy of the lucent area demonstrated inflammation and necrosis but no organisms were seen. During a six-week course of pyrimethamine, sulfadiazine, and folinic acid therapy there was clinical and neuroradiologic resolution. The short course of therapy as well as the inadvertent substitution of folic acid for folinic acid and trimethoprim-sulfamethoxazole for sutfadiazine resulted in the reappearance of neurologic deficits. Reinstitution of appropriate therapy produced gradual improvement over a nine-month period. Serial computed tomography scans correlated with the clinical course. In the immunologically compromised host CNS toxoplasmosis should be considered in the differential diagnosis of an evolving CNS syndrome. Early detection and prolonged therapy with appropriate drugs can result in a favorable outcome. Computed tomography scanning may be helpful in diagnosis and follow-up.