Hashimoto encephalopathy as manifestation of central nervous system chronic graft‐versus‐host disease after hematopoietic stem cell transplantation

To the Editor:We present a case of Hashimoto encephalopathy (HE) as a manifestation of central nervous system (CNS) chronic graft-versushost disease (GvHD) after hematopoietic stem cell transplantation (HSCT). A 12-year-old male diagnosed with hyper-IgM syndrome underwent allogeneic HSCT using bone marrow of his human leukocyte antigen-identical sibling. Conditioning consisted of busulfan and cyclophosphamide and GvHD prophylaxis of cyclosporine and metothrexate. At 6months after transplant, he developed liver chronic GvHD confirmed by a biopsy. The patient was started on corticosteroids, photopheresis, and etanercept showing with partial response. One year later, hewas admitted to the transplant unit due to continuous myoclonus of the left lower extremity. Cerebrospinal fluid (CSF) was acellular with increased protein level (90 mg/dL). CSF opening pressurewas normal.Microbiological blood andCSF studies and cytology were negative. Cranial magnetic resonance imaging (MRI) with gadolinium showed vasogenic edema in the left frontal hemisphere. Anticonvulsants were started without improvement of the myoclonus. The patient worsened to a state of tetraplegia and aphasia, with locked-in syndrome. Patient was transferred to the intensive care unit due to decreased