Segmental Myoclonus and Epilepsy in a Child with GAD 65 Antibodies

Elevated GAD 65 antibodies have diverse clinical associations, including stiff person syndrome (SPS), cerebellar ataxia, limbic encephalitis, epilepsy, ocular motor disorders, type 1 diabetes mellitus,1,2 and rarely myoclonus.3–6 GAD 65 antibody-associated neurological syndromes, mostly SPS or epilepsy, are rarely reported in pediatrics.2,7 Many patients improve after immune therapy and some, whose presentation includes seizures, become seizure free.1 Elevated GAD 65 antibodies may be associated with tumors. Blood tests were normal including CBC, extended electrolytes, glucose, liver and thyroid function, uric acid, copper, ceruloplasmin, ESR, CRP, C3, C4, immunoglobulins, rheumatoid factor, ANCAs, anti-TPO, and phospholipid (cardiolipin and β2-glycoprotein) antibodies. Whole-body positron emission tomography (18 F FDG-PET) to further look for potential neoplasm showed intense asymmetric activity, right > left, in the nasopharynx and oropharynx from the myoclonus. Four months after presentation, she was started on immunosuppressive therapy according to the BrainWorks protocol (http://www.sickkids.ca/PDFs/Research/BrainWorks/63976-Antibody%20IBrainD.pdf): IV methylprednisolone pulse therapy for 5 d (30 mg/kg), followed by oral taper of prednisone over 5 months (initial dose 2 mg/kg), 8 courses in total (5 biweekly then 3 monthly) IV immunoglobulins (2 g/kg/course), and 2 doses of rituximab (500 mg/m2) 2 weeks apart.