Sex Differences among Populations in the Association between PTPN22 and Type 1 Diabetes. An analysis of the Effect of Maternal Age at Delivery and of Age at Onset of Disease

The association between PTPN22 genetic polymorphism and Type 1 Diabetes has been observed in some populations in females only. To elucidate the causes of these differences among populations we have examined two populations taking into account maternal age at delivery and age at onset of the disease. We have examined 376 children with T1D from Continental Italian population and in 248 children with T1D from Sardinian population. In children aging 6 years or less at onset of T1D an increase of *T carriers in T1D females as compared to males is observed in Sardinia only. No difference between sexes is observed in children aging more than 6 years at onset. In children delivered by mothers aging 32 years or less the proportion of *T allele carriers is higher in females than in males in both populations. In children delivered by mothers aging more than 32 years the proportion of *T allele carriers is higher in females as compared to males in Sardinia only. Differences in the genetic background and environmental conditions between Continental Italy and Sardinia affect the age at onset and the relationship between maternal age at delivery and risk of T1D. The effect of these variables are influenced by sex thus giving some clue to explain the sex differences in the association between T1D and PTPN22 observed in some populations.