The c.710A>G variant in the HNF1 homeobox A gene, HNF1A, causes an amino acid change of asparagine to serine at codon 237 (p.(Asn273Ser)) of NM_000545.8. This variant is located within a conserved region of the DNA binding domain (codons 107-174 and 201-280) of HNF1A, which is defined as critical for the protein’s function by the ClinGen MDEP (PM1_Supporting). This variant is predicted to be deleterious by computational evidence, with a REVEL score of 0.706, which is greater than the MDEP VCEP threshold of 0.70 (PP3) and is absent from gnomAD v2.1.1 (PM2_Supporting). Another missense variant, c.709A>G (p.Asn237Asp) has been classified as likely pathogenic by the ClinGen MDEP (PM5_Supporting). This variant was identified in an individual with a clinical history highly specific for HNF1A-MODY (MODY probability calculator result >50%, negative genetic testing for HNF4A, and response to low-dose sulfonylurea) (PP4_Moderate; internal lab contributors). This variant was identified in three unrelated individuals with non-autoimmune and non-absolute/near-absolute insulin-deficient diabetes; however, PS4_Moderate cannot be applied because this number is below the ClinGen MDEP threshold (internal lab contributors). In summary, c.710A>G 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, approved 9/30/21): PM1_Supporting, PM2_Supporting, PP4_Moderate, PM5_Supporting, PP3.