Cerebral toxoplasmosis after hematopoietic stem cell transplantation: A case series from a developing country

Toxoplasma gondii infection after hematopoietic stem cell transplantation (HSCT) is rare but potentially fatal, with reported incidences ranging from 0.8% to 8%, largely influenced by regional seroprevalence. In Latin America, where seroprevalence exceeds 50% and atypical parasite genotypes circulate, reactivation appears more frequent and may present with greater severity. The interaction between local epidemiology, immune reconstitution, and prophylaxis strategies remains poorly characterized. We conducted a descriptive case series of HSCT recipients diagnosed with cerebral or ocular toxoplasmosis at a high-seroprevalence Latin American center between 2017 and 2025. Among 1178 HSCT procedures (572 allogeneic and 606 autologous), 12 patients developed toxoplasmosis, corresponding to cumulative incidences of 1.75% in allogeneic and 0.33% in autologous recipients. Median age was 23.5 years (15.5–37), and median time from HSCT to clinical presentation was 123 days (42.5–160.5). Most patients had acute leukemia or aplastic anemia and had undergone haploidentical allogeneic transplantation. Polymerase chain reaction of cerebrospinal fluid or ocular samples confirmed infection in most cases. Neuroimaging typically demonstrated multifocal supra- and infratentorial lesions. Concomitant cytomegalovirus reactivation and graft-versus-host disease were frequent. Primary prophylaxis with trimethoprim–sulfamethoxazole was inconsistently administered due to early onset of disease or clinical contraindications. Cerebral toxoplasmosis after HSCT remains an uncommon but life-threatening complication in high-seroprevalence settings. Regional parasite diversity, immune recovery dynamics, and barriers to timely prophylaxis underscore the need for context adapted surveillance and prevention strategies in Latin American transplant populations. • Atypical toxoplasma strains require further characterization to determine virulence severity. • Enhanced surveillance, timely testing, and adapted prophylaxis are essential in HSCT. • In endemic regions, concurrent prevention of toxoplasmosis and CMV is essential given their shared high prevalence.Toxoplasma PCR monitoring should be considered in high prevalence areas.