Anti-glutamic acid decarboxylase (GAD) positive cerebellar Ataxia with transitioning to progressive encephalomyelitis with rigidity and myoclonus (PERM), responsive to immunotherapy: A case report and review of literature

We present a case of a 65-year-old African American male, immunosuppressed on Tacrolimus, who initially presented with cerebellar ataxia and rapidly developed Progressive Encephalomyelitis with Rigidity and Myoclonus (PERM) with positive anti-glutamic acid decarboxylase (GAD65) antibodies, no underlying malignancy, and normal neuroimaging. PERM is a rare spectrum of Stiff Person Syndrome (SPS), which is strongly associated with anti-GAD antibodies and characterized by flare-ups and remissions of encephalopathy, myelopathy and rigidity with myoclonus. PERM is diagnosed clinically and has been successfully treated with both Intravenous Immunoglobulin (IVIg) and plasmapheresis. Our patient was successfully treated with IVIg. On day 14 after starting IVIg treatment, his neurological symptoms started to improve and ultimately returned to baseline.