MANF concentrations in serum samples derived from 1–9-year-old patients with recent onset T1D (n = 98, sample taken within 0–22 days from the clinical diagnosis) were analyzed along with two age-matched control groups, one comprising non-diabetic siblings testing positive for two to five of the diabetes-predictive autoantibodies analyzed (n = 48), and the other being autoantibody-negative (n = 48). Here, MANF is linked to type 1 diabetes mellitus.