Multiplex family with GAD65-Abs neurologic syndromes

OBJECTIVE: Neurologic autoimmune syndromes associated with anti–glutamate acid decarboxylase 65 antibodies (GAD65-Abs) are rare and mostly sporadic. METHODS: We describe a niece and her aunt with GAD65-Abs neurologic syndromes. High-resolution HLA typing of Class I and Class II alleles was performed using next-generation sequencing. RESULTS: The proband had cerebellar ataxia and probable limbic encephalitis features, whereas her niece had stiff-person syndrome. Both had a high titer of GAD65-Abs in serum and CSF and showed signs of inflammation in CSF. Both affected members carried the same rare recombinant DRB1*15:01:01∼DQA1*01:02:01∼DQB1*05:02:01 haplotype, which may or may not be involved in disease susceptibility. Of interest, other unaffected members of the family either had the same HLA haplotype but normal serum GAD65-Abs or had different HLA types but a high titer of serum GAD65-Abs without neurologic symptoms, suggesting cumulative effects. CONCLUSIONS: This unique association strengthens the concept that hereditary factors, possibly including specific HLA haplotypes, play a role in neurologic syndromes associated with GAD65-Abs.