The c.1136C>G variant in the glucokinase gene, GCK, causes an amino acid change of alanine to glycine at codon 379 (p.(Ala379Gly)) of NM_000162.5. GCK is defined by the ClinGen MDEP VCEP as a gene that has a low rate of benign missense variation and where pathogenic missense variants are a common mechanism of disease (PP2). This variant is predicted to be deleterious by computational evidence, with a REVEL score of 0 0.922, which is greater than the MDEP VCEP threshold of 0.70 (PP3). This variant is absent from gnomAD v2.1.1 (PM2_Supporting). Two other missense variants, c.1136C>A p.Ala379Glu and c.1136C>T p.Ala379Val, have been classified as likely pathogenic by the ClinGen MDEP VCEP (PM5_Supporting). This variant was identified in an individual with a clinical history highly specific for GCK-hyperglycemia (FBG 5.5-8 mmol/L and HbA1c 5.6 - 7.6% and negative antibodies) (PP4_Moderate, internal lab contributors). In summary, this variant meets the criteria to be classified as likely pathogenic for monogenic diabetes. ACMG/AMP criteria applied, as specified by the ClinGen MDEP VCEP (specification version 1.3.0, approved 8/11/2023): PP4_Moderate, PP2, PP3, PM2_Supporting, PM5_supporting.