The c.1396T>C variant in the glucokinase gene, GCK, is causes an animo acid change at the stop codon of the final exon (10/10), resulting in the addition of 144 amino acids at the end of the protein (p.(Ter466ArgextTer144)). This variant, located in exon 10 of 10, is predicted to cause loss of a stop codon and result in an elongated protein. The additional residues are expected to cause improper folding, resulting in loss of function in a gene in which loss-of-function is an established disease mechanism (PVS1; PMID 19790256). This variant is absent in gnomAD v2.1.1 (PM2_Supporting). This variant was identified in an individual with a clinical picture consistent with non-autoimmune/insulin-dependent diabetes, however PS4_moderate cannot be applied because this number is below the MDEP threshold (internal lab contributor). This variant was identified in an individual with a phenotype suggestive of GCK-hyperglycemia; however, PP4 is unable to be evaluated due to insufficient clinical information (internal lab contributors). In summary, c.1396T>C meets the criteria to be classified as likely pathogenic for monogenic diabetes. ACMG/AMP criteria applied, as specified by the ClinGen MDEP (specification version 1.2.0, approved 6/7/2023): PVS1, PM2_Supporting.