Primary CNS post-transplant lymphoproliferative disorder following haploidentical HSCT using post-transplant high-dose cyclophosphamide

Neurological complications after hematopoietic stem cell transplantation (HSCT) are frequently life-threatening, and their clinical management can be highly challenging. In the case of central nervous system lesions post-HSCT, a definitive diagnosis is often difficult to reach because many different causative and contributing conditions may be present, including bacterial, fungal, or viral infections; original disease relapse; and post-transplant lymphoproliferative disorder (PTLD). Here, we report a case of a 32-year-old male patient with Philadelphia chromosomepositive acute lymphoid leukemia who underwent three HSCTs and was then diagnosed with primary central nervous system (PCNS) PTLD by brain biopsy. The third HSCT was a haplo-identical peripheral blood stem cell transplantation from his mother, with post-transplant high-dose cyclophosphamide and tacrolimus used as graft-versus-host disease prophylaxis. Four months after the HSCT, multiple small ring lesions were detected in the parabasal ganglia of the patient's brain during magnetic resonance imaging. A lesion biopsy indicated Epstein-Barr virus (EBV)-positive, diffuse large B-cell lymphoma. Because the patient had no evidence of systemic lymphadenopathy, we diagnosed him with PCNS-PTLD. There was no EBV DNA in this patient's cerebrospinal fluid. The diagnosis of PCNS-PTLD by EBV DNA polymerase chain reaction is difficult and highlights the importance of a brain biopsy to diagnose PCNS-PTLD, especially in cases showing no EBV DNA in the cerebrospinal fluid. Although a rare condition, it is essential to locate and analyze cases of PCNS-PTLD after HSCT to establish the optimal strategy for treatment or prophylaxis.