MODY 3 (HNF1A) Autosomal Dominant Inheritance

A 22-year-old lean woman (BMI 22 kg/m²) presents with incidental hyperglycemia (fasting glucose 168 mg/dL, HbA1c 8.2%) on routine screening. She has no polyuria, polydipsia, weight loss, or acanthosis nigricans. Fasting C-peptide is preserved at 1.8 ng/mL, and diabetes autoantibodies (GAD, IA-2, ZnT8) are negative. Her three-generation pedigree is shown in the diagram marked **A**, demonstrating vertical transmission across generations with male-to-male transmission and approximately 50% of offspring affected. No skipped generations are observed. A targeted monogenic diabetes panel confirms a heterozygous pathogenic HNF1A mutation. Which of the following inheritance patterns BEST describes the pedigree pattern marked **A** and is consistent with MODY 3?