Clinical spectrum of glutamic acid decarboxylase antibodies in a Taiwanese population.

Abstract

High levels of autoantibodies against glutamic acid decarboxylase (GAD-abs) are associated with stiff-person syndrome (SPS). However, the full clinical spectrum associated with GAD-abs in Asians is unclear. The clinical and immunological features of patients positive for GAD-abs were reviewed in a large Taiwanese series. Retrospective case series and immunological investigations were conducted between July 2007 and July 2017 at a tertiary referral centre in Taiwan. Amongst 361 patients with GAD-ab reactivity, 185 with detailed clinical records were included. Twenty-seven patients (14.59%), with a mean age at assessment of 54.8±13.9years, presented with neurological symptoms. The major neurological presentations (mean GAD-ab concentrations) were SPS (n=9, 33.3%; 135.45±27.84U/ml), cerebellar ataxia (n=3, 11.1%; 95.61±49.63U/ml), encephalopathy (n=2, 7.4%; 51.8±49.64U/ml) and epilepsy (n=1, 3.7%; 83.3U/ml). Notably, eight patients fulfilling the clinical diagnosis of multiple system atrophy had relatively lower GAD-ab concentrations (2.57±0.82U/ml), which has not been reported previously. There was no correlation between disease severity and GAD-ab concentration. Patients presenting with comorbid endocrinopathies (n=15, 55.5%) had higher GAD-ab concentrations than those without endocrinopathies (n=12, 44.4%; 104.45±22.51U/ml vs. 34.08±21.83U/ml, P=0.04). Of 158 patients (85.4%) without a neurological presentation, 133 had type 1 diabetes mellitus and 20 had diabetes of other aetiologies (type 2 or gestational diabetes mellitus, or diabetes secondary to pancreatitis); the remaining four patients had pure thyroid disorders. A clinical and immunological evaluation of East Asian patients positive for GAD-abs is presented and a different clinical spectrum of anti-GAD syndrome is identified compared to Caucasians.