The c.604A>G variant in the glucokinase gene, GCK, causes an amino acid change of methionine to valine at codon 202 (p.(Met202Val)) 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 absent from gnomAD v2.1.1 (PM2_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 persistent impaired fasting glucose) (PP4_Moderate; internal lab contributors). Another missense variant, c.605T>C p.Met202Thr, has been classified as pathogenic by the ClinGen MDEP but has a greater Grantham distance than p.Met202Val (PM5_Supporting). This variant was identified in three unrelated individuals with hyperglycemia; however, PS4_Moderate cannot be applied because this number is below the ClinGen MDEP threshold (ClinVar, internal lab contributors). This variant segregated with diabetes with one informative meiosis in a single family; however, this does not meet the thresholds for PP1 set by the ClinGen MDEP (PMID: 27236918, internal lab contributors). This variant has a REVEL score of 0.596, which is between the ClinGen MDEP thresholds for BP4 and PP3, predicting neither a damaging nor benign impact on GCK function. In summary, c.604A>G meets the criteria to be classified as uncertain significance for monogenic diabetes. ACMG/AMP criteria applied, as specified by the ClinGen MDEP (specification version 1.3.0, approved 8/11/2023): PM2_Supporting, PM5_Supporting, PP2, PP4_Moderate.