Context and objective: Pathogenesis of autoimmune thyroid disease (ATD) is multifactorial. Hp infection has been proposed to be involved in non gastrointestinal conditions and reported more frequent in ATD-adult patients.

We evaluated the prevalence of Hp antibodies in young ATD-patients and investigated on the possibility that a susceptible immunogenetic profile could influence the development of ATD in subjects with Hp infection.

Subjects and methods: We retrospectively studied 90 children with ATD (median age 11.2 yr), 70 age and sex-matched healthy subjects as controls and 65 patients with Turner syndrome (TS) (median age 18.8 yr).

Antibodies to Hp were determined at diagnosis in ATD-patients and, in Turner patients, at the last control in cases without ATD and before the appearance of thyroid autoantibodies in the others. Serological and molecular HLA typing for class I and II polymorphisms was performed.

Results: Prevalence of positive Hp serology resulted significantly higher in ATD-patients than in controls (P = 0.032). No association was found between individual HLA alleles and Hp serology. HLA-A1, B8 and DRB1*0301 were found significantly associated to ATD. A significant interaction between HLA-DRB1*0301 and Hp infection was present in ATD-patients and not in controls (P = 0.007), suggesting that the copresence of these two factors might favor ATD development. Similar phenomenon was observed in TS patients (P = 0.02), cumulative Mantel test P = 0.0001.

Conclusions: Another target of Hp-elicited immune-inflammatory response might be thyroid gland in subjects with a peculiar immunogenetic profile so that ATD may be a consequence. Our findings suggest the opportunity of eradicating Hp infection in children with ATD and/or with susceptible HLA alleles.