Clinical spectrum of glutamic acid decarboxylase antibodies in a Taiwanese population

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 ± 13.9 years, presented with neurological symptoms. The major neurological presentations (mean GAD-ab concentrations) were SPS (n = 9, 33.3%; 135.45 ± 27.84 U/ml), cerebellar ataxia (n = 3, 11.1%; 95.61 ± 49.63 U/ml), encephalopathy (n = 2, 7.4%; 51.8 ± 49.64 U/ml) and epilepsy (n = 1, 3.7%; 83.3 U/ml). Notably, eight patients fulfilling the clinical diagnosis of multiple system atrophy had relatively lower GAD-ab concentrations (2.57 ± 0.82 U/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 ± 22.51 U/ml vs. 34.08 ± 21.83 U/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.