Toxoplasmosis After Hematopoietic Stem Cell Transplantation

TLDR: In univariate and multivariate analyses, having received adequate therapy and experiencing late infection (>63 days after HSCT) were associated with a lower risk of dying from toxoplasmosis.

Abstract: In immunocompromised individuals, toxoplasmosis mostly occurs as a reactivation of a latent infection, causing severe to life-threatening disease. Thus, recipients who are seropositive for Toxoplasma gondii before an allogeneic hematopoietic stem cell transplant (HCT) are at highest risk, although primary infections may also cause severe toxoplasmosis. The disease most often affects the central nervous system, but in HCT recipients other organs are involved in more than half of the cases. Because of the alteration of the immune response in these patients, serodiagnosis is not sufficiently reliable in the diagnosis of post-HCT toxoplasmosis, and direct detection of the causative agent is required for an etiologic diagnosis (ideally by microscopy, but most commonly through detection of its DNA by PCR). If inadequately treated or left untreated, toxoplasmosis generally has a fatal outcome in HCT recipients. Therefore, treatment must be started as early as possible. However, due to the high mortality of established disease, preemptive treatment using routine blood PCR monitoring seems effective in detecting infection early and preventing disease, especially in seropositive high-risk alloHCT recipients when chemo-prophylaxis is not possible. The gold standard both in the treatment of reactivation and disease is the combination of pyrimethamine–sulfadiazine–folinic acid, while cotrimoxazole is the agent of choice in the primary prophylaxis for high-risk patients.