Toxoplasma infection after human allogeneic bone marrow transplantation: clinical and serological study of 80 patients.

Systematic clinical and serological studies to evaluate the frequency of toxoplasmosis in bone marrow transplant recipients were performed in 80 consecutive patients. Antitoxoplasma antibody titres were measured in donors and recipients before transplant and subsequently post-transplant. Before bone marrow transplant, 54 recipients were seropositive and 26 were seronegative, whereas 35 donors were seropositive and 45 were seronegative. After bone marrow transplant, the frequency of clinical and serological manifestations of toxoplasmosis appeared closely related to the recipient's serological status before transplant. In the seronegative group of patients before transplant the incidence of toxoplasmosis was low: only two patients experienced seroconversion 3 months after bone marrow transplant and one developed clinical symptoms consistent with toxoplasmosis but without cerebral involvement. Clinical toxoplasmosis or secondary elevation of antibody titres was mostly observed in pre-bone marrow transplant seropositive patients; in this group, cerebral toxoplasmosis occurred in four patients and a significant secondary rise of antibody titres was observed in 16 patients. It thus appears that toxoplasmosis is most often related to a reactivation of latent cysts. Prophylactic treatment may be useful in patients presenting serological evidence of past or latent infection before bone marrow transplant.