Toxoplasma-induced hemophagocytic lymphohistiocytosis after haploidentical allogeneic stem cell transplantation.

Hemophagocytic lymphohistiocytosis (HLH) is a disorder of immune regulation, manifested by fever, pancytopenia, hyperferritiniemia, hypertriglyceridemia, and extensive hemophagocytosis involving the bone marrow and spleen. HLH can occur in adults with an underlying hematopoietic malignancy, or with systemic infections. HLH following hematopoietic stem cell transplantation (HSCT) is unusual, and the diagnosis may be challenging particularly because the diagnostic criteria in the HLH-2004 guidelines overlap with common post-transplant complications such as engraftment syndrome, graft-vs-host disease, and infections. HLH is commonly triggered by viral, bacterial and, less commonly, parasitic infections. Following HSCT, patients with latent Toxoplasma infection may develop systemic disease secondary to reactivation, and rarely this may lead to a HLH physiology, with a very high mortality rate. Herein we describe the successful management of disseminated toxoplasmosis associated with life-threatening HLH using tocilizumab and antimicrobial therapy.