The c.627_628delinsAG variant in the glucokinase gene, GCK, is a deletion of GA followed by an insertion of AG, resulting in an amino acid change of methionine to valine at codon 210 (p.(Met210Val)) 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 in gnomAD v2.1.1 (PM2_Supporting), and was identified in an individual with a clinical history highly specific for GCK-MODY (FBG 5.5-8 mmol/L and HbA1c 5.6 - 7.6%) (PP4; internal lab contributor). Additionally, two other missense variants, c.629T>A (p.Met210Lys) and c.629T>C (p.Met210Thr), have been classified as pathogenic by the ClinGen MDEP (PM5_Strong). In summary, c.627_628delinsAG meets the criteria to be classified as likely pathogenic for monogenic diabetes. ACMG/AMP criteria applied, as specified by the ClinGen MDEP (specification version 1.1.0, approved 3/23/2023): PM5_Strong, PP2, PP4, PM2_Supporting.