The c.1373_1384del variant in the glucokinase gene, GCK, is a 12 base pair deletion resulting in the in-frame deletion of 4 amino acids at codon 458 (p.(Lys458_Cys461del)) within exon 10 of NM_000162.5. The c.1373_1384del variant is predicted to change the length of the protein due an in-frame deletion of 4 amino acids in a nonrepeat region (PM4). Additionally, this variant is absent in gnomAD v2.1.1 (PM2_Supporting). This variant was identified in 3 unrelated individuals with non-autoimmune/insulin-deficient diabetes; however, this number does not meet the MDEP cutoff for PS4_Moderate (PMID: 30105470; internal lab contributor). This variant is present in an individual reported to have GCK-MODY; however, there was insufficient information to evaluate for PP4 (PMID: 30105470). This variant segregates with disease with 3 meioses in 2 families with MODY (PP1_Moderate; PMID 30105470). In summary, c.1373_1384del meets the criteria to be classified as VUS for monogenic diabetes. ACMG/AMP criteria applied, as specified by the ClinGen MDEP (specification version 1.2.0, approved 6/7/2023): PM4, PM2_Supporting, PP1_Moderate.