This pattern of association was the same for all nine CpGs with significant mediator–exposure interaction terms, including cg02946697, cg08285446, cg24513387, and cg25674613 near CTD-2281E23.1; cg00565786 and cg27509052 near CTD-2281E23.2; and cg11192059, cg22763586, and cg27351978 near DLGAP2. No probes within the HOPX nonimprinted control region showed evidence of differential effects of methylation on T1D risk by family history of T1D (all exposure ∗ mediation interaction P > 0.1). Here, HOPX is linked to type 1 diabetes mellitus.