To estimate the prevalence of neurological anti-GAD autoimmunity in Martinique (French West Indies) on January 1^st 2016.

Anti-Glutamic Acid Decarboxylase antibodies (anti-GAD abs) have been lately associated with rare heterogeneous neurological syndromes. Within anti-GAD autoimmunity, prevalence of Stiff Person Syndrome (SPS) is only known and estimated to be about 1 to 2 cases per 10⁶ inhabitants (inhab.). On the other hand, prevalence rates of Cerebellar Ataxia (CA), Late-Onset focal epilepsy (LOFE), Limbic Encephalitis (LE), Progressive encephalomyelitis with rigidity and myoclonus (PERM) are unknown.

Data were collected from 1993 to February 2019. Patients were identified through hospitalized based medical records. Each included patient had neurological manifestations associated with high levels of anti-GAD abs. The primary end point was the calculation of the prevalence of all neurological syndromes associated with anti-GAD autoimmunity.

On January 1^st 2016, 21 patients had neurological syndromes associated with anti-GAD autoimmunity. The overall prevalence of anti-GAD auto-immunity was 55.78 cases per 10⁶ (CI 95 % +/- 23.85) inhab.

Among those patients, 13 had SPS (prevalence = 34.53/10⁶  (CI 95% +/- 18.77) inhab.) , 9 had CA (prevalence = 23.91/10⁶  (CI 95% +/- 15.62) inhab.) , 6 had LOFE (prevalence = 15.94/10⁶  (CI 95% +/- 15.62) inhab.), 5 had LE (prevalence = 13.28/10⁶  (CI 95% +/- 11.64) inhab.), and 1 PERM (prevalence = 2.66/10⁶  (CI 95% +/- 5.21) inhab.).

Our study is the first estimating prevalence of each neurological syndromes lying within the entire spectrum of  anti-GAD auto-immunity. SPS prevalence in Martinique is 34 times higher to that previously reported elsewhere. Further studies are required focusing on frequency of anti-GAD autoimmunity in people of African ancestry.