In 2 brothers with TNDM diagnosed with diabetes in 2010 (first observation period) and 2017 (second observation period) compound heterozygous variants of ABCC8 (NM_000352.6: c.4412-13G>A, p. ?; c.1619C>T, p.Thr540Ile) (Table 2) were detected. This evidence concerns the gene ABCC8 and transient neonatal diabetes mellitus.