The c.524G>A variant in the glucokinase gene, GCK, causes an amino acid change of glycine to glutamate at codon 175 (p.(Gly175Glu)) of NM_000162.5. GCK is defined by the ClinGen MDEP as a gene that has a low rate of benign missense variation and has pathogenic missense variants as a common mechanism of disease (PP2). This variant is predicted to be deleterious by computational evidence, with a REVEL score of 0.914, which is greater than the MDEP VCEP threshold of 0.70 (PP3). This variant is absent from gnomAD v2.1.1 (PM2_Supporting). This variant was identified in four unrelated individuals with hyperglycemia (PS4_Moderate; PMID: 11508276, internal lab contributors). This variant was identified as a de novo occurrence with unconfirmed parental relationships in one individual with a clinical picture consistent with GCK-hyperglycemia (FBG 5.5-8 mmol/L and HbA1c 5.6-7.6) (PS2_Moderate; internal lab contributors). 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%) (PP4; internal lab contributors). Another missense variant, c.523G>A p.Gly175Arg, has been classified as pathogenic by the ClinGen MDEP but has a greater Grantham distance than p.Gly175Glu (PM5_Supporting). In summary, c.524G>A meets the criteria to be classified as likely pathogenic for monogenic diabetes. ACMG/AMP criteria applied, as specified by the ClinGen MDEP (specification version 1.3.0, approved 8/11/2023): PS4_Moderate, PS2_Moderate, PP4, PM2_Supporting, PP2, PP3, PM5_Supporting.