[Multifocal motor neuropathy following allogeneic hematopoietic stem cell transplantation for mixed-phenotype acute leukemia].

A 56-year-old woman with mixed-phenotype acute leukemia underwent allogeneic hematopoietic stem cell transplantation (allo-HSCT). She developed grade 2 acute graft-versus-host disease (GVHD), which subsequently improved, but did not develop chronic GVHD. Immunosuppressive therapy was discontinued 7 months after allo-HSCT, with no relapse of GVHD. However, around the same time, the patient began experiencing generalized fatigue, left eyelid ptosis, and right upper limb finger extensor weakness. Further examinations led to a diagnosis of Hashimoto's disease and multifocal motor neuropathy (MMN). Although neurological impairment was progressive, muscle strength improved after treatment with high-dose intravenous immunoglobulin therapy for MMN and blinatumomab for post-transplant relapse of MPAL. The clinical course suggests that MMN developed after allo-HSCT as an immune-mediated neuropathy involving donor lymphocytes. It may be appropriate to consider MMN as a differential diagnosis for peripheral neuropathy occurring after discontinuation of immunosuppressive agents or in association with autoimmune disease.