Hemophagocytic syndrome following haploidentical peripheral blood stem cell transplantation with post-transplant cyclophosphamide.

Hemophagocytic syndrome (HPS) is a rare but serious complication after allogeneic transplantation which has been reported to be particularly high after unrelated cord blood transplantation. We report on the incidence, risk factors and outcome of HPS in 51 patients (age 2-64 years) after haploidentical peripheral blood stem cell (PBSC) transplantation with post-transplantation cyclophosphamide (PTCY). The incidence of HPS was 12.2 %, occurring at a median of 18 days. The non-relapse mortality in patients with HPS was 83.3 % compared to 11.6 % in patients without HPS. Complete donor chimerism was documented in all patients with HPS. Definite infective etiology was identified in two patients only. The others were refractory to multiple lines of treatment and 3 patients underwent a second transplant. Even though the symptoms and biochemical markers of HPS showed prompt response in 2/3 patients undergoing a second allograft, they succumbed to infections before haematological recovery. The others succumbed to multi-organ failure or infections. Age < 10 years, transplantation for non-malignant disease and high CD34 content of the graft were identified as risk factors for HPS. Considering the fact that post-transplant HPS is usually a refractory and fatal condition, we discuss further attempts at deciphering the pathogenesis, developing modalities to prevent this complication and improve the outcome.