To report an expanded spectrum of Gad-65 Associated autoimmune encephalitis in pediatric patients.

GAD-65 antibodies associated autoimmune encephalitis (AIE) is rare in the pediatric population. Diagnosis of GAD encephalitis requires the child to have clinical features consistent with pediatric AIE in the presence of GAD antibody in the cerebrospinal fluid (CSF). GAD- 65-associated AIE is typically very refractory to the first line immune therapies with high rates of relapse. We describe a series of children with serum GAD- 65 associated AIE that present in the absence of antibodies to GAD-65 in the CSF. Their presentation and response to therapy are comparable to those with CSF positivity. This finding extends the spectrum of GAD-65 associated AIE to include patients that are CSF antibody negative.

A retrospective analysis of clinical features, diagnostic tests and response to therapy was conducted on patients diagnosed with autoimmune encephalitis that were positive for GAD 65 antibodies in the serum.

Six patients with were diagnosed with GAD-65 AIE but had normal CSF.  Median age at presentation was 12.5 years, with 67% patients being male. All patients presented with mental status and behavior changes, two thirds with movement disorders, one in refractory status epilepticus and another one developed seizures later in course of disease. Two patients had abnormal EEGs and only one had an abnormal MRI. All patients treated with steroids and intravenous immunoglobulin (IVIG) had good initial response. However all patients relapsed and were placed on maintenance therapy with Rituximab and later needing plasmapheresis for refractory relapses. Tumor screening remained negative for these patients.

AIE secondary to serum GAD 65 antibodies can present similar to children which AIE secondary to the same antibodies in the CSF. Treating these children with early immunotherapy may help achieve better neurological outcomes.