Significant improvement following combination treatment with mefloquine and mirtazapine in a patient with progressive multifocal leukoencephalopathy after allogeneic peripheral blood stem cell transplantation.

We report a case of a 40-year-old female who developed progressive multifocal leukoencephalopathy (PML), which is associated with JC virus reactivation, after allogeneic hematopoietic cell transplantation. As she had been suffering from graft-versus-host disease and lung damage after pneumocystis pneumonia, the administration of calcineurin inhibitor and steroid could not be discontinued. However, she showed a favorable improvement in clinical symptoms and imaging findings after treatment with the anti-malarial drug, mefloquine and a serotonin receptor blocker, mirtazapine. Continuation of the treatment for eight months finally led to the clearance of the JC virus from her cerebrospinal fluid. She currently shows no neurological disturbance and has resumed her daily activities. PML due to the severe immunosuppressive condition has been reported as a fatal complication after allo-SCT. Our case suggests that combination treatment with mefloquine and mirtazapine may be of great value for the treatment for PML patients in the post allo-SCT setting, although it is difficult to say whether the combination treatment alone led to improvement. Further clinical study is needed to clarify the efficacy of these drugs for the treatment of PML.