As secondary outcomes, we assessed the optimal anti-TTG IgA upper limit of normal (ULN) cutoff for sparing biopsy, and personal and familial autoimmunity history in the individuals with T1D and CD (T1D-CD) compared with T1D-only.<h4>Methods</h4>In this retrospective observational study, among 6933 individuals with T1D onset (2010-2019), 556 were grouped according to CD onset: before (CD_FIRST), concomitant (CD_CONCOMITANT), or after T1D (T1D_FIRST), and compared with 141 T1D without CD. This evidence concerns the gene CD79A and Autoimmunity.