Myasthenia gravis is among the rare complications after allogeneic hematopoietic stem cell transplantation and is usually associated with chronic GVHD. Herein, we report a 2-year and 10 months of age female with Griscelli syndrome, who developed severe myasthenia gravis at post-transplant +22nd month and required respiratory support with mechanical ventilation. She was unresponsive to cyclosporine A, methylprednisolone, intravenous immunoglobulin, and mycophenolate mofetil and the symptoms could only be controlled after plasma exchange and subsequent use of rituximab, in addition to cyclosporine A and mycophenolate mofetil maintenance. She is currently asymptomatic on the 6th month of follow-up. Pediatr Blood Cancer 2014;61:928-930. (c) 2013 Wiley Periodicals, Inc.