Serological analysis of gluten-related antibodies in idiopathic neuropathies and cerebellar ataxia

Immune reactivity to gluten in the development of peripheral neuropathies and cerebellar ataxia has been suggested for decades, but evidence is scarce. The aim of the current study was to test the prevalence of tissue transglutaminase 2 (anti-TG2), tissue transglutaminase 6 (anti-TG6), and gliadin antibodies (anti-gliadin) in a large cross-sectional study. The sera of patients with idiopathic cerebellar ataxia, idiopathic small fibre neuropathy (SFN) and chronic idiopathic axonal polyneuropathy (CIAP), and controls with a comparable age distribution and men/women ratio were collected. The sera were analysed for anti-gliadin IgA/IgG (manufacturer's and lower cut-off), anti-TG2 IgA and anti-TG6 IgA/IgG. In total, 683 samples were analysed: 476 patients (249 SFN, 161 CIAP and 66 idiopathic cerebellar ataxia) and 195 controls. There were no differences between disease and control group in the prevalence of elevated anti-TG6, anti-TG2 and anti-gliadin using the manufacturer's cut-off. Using a lower cut-off of 3 U/mL, previously used by others for gluten-related neurological disorders, anti-gliadin IgA was positive in 20.8% patients vs 12.8% controls (p = 0.017) and anti-gliadin IgG in 7.6% vs 2.6% (p = 0.013), respectively. In subgroup analyses, significant differences were only observed in SFN for anti-gliadin IgA and in idiopathic cerebellar ataxia for anti-gliadin IgG using this lower cut-off after adjusting for sex and age. In conclusion, no difference in anti-TG2, anti-TG6 and anti-gliadin levels were observed between patients and controls. Only when using the lower cut-off (3 U/mL), the patients with SFN and idiopathic cerebellar ataxia were more often positive for anti-gliadin than controls. Whether these low-titre antibodies are gluten related, have any pathophysiological relevance, or reflect an epiphenomenon of neurodegeneration or gut inflammation is unknown.