A 24-year-old lean woman has fasting glucose of 118 mg/dL diagnosed at age 20 years. Her mother and maternal grandmother were diagnosed with mild diabetes before age 25 and have never developed ketoacidosis. She is not obese, has no acanthosis nigricans, anti-GAD65 antibodies are negative, and fasting C-peptide is detectable. Her HbA1c is 6.9%. Which is the most likely diagnosis?

• A Type 1 diabetes mellitus
• B Latent autoimmune diabetes of adults
• C Type 2 diabetes mellitus with early beta cell failure
• D Maturity onset diabetes of the young, HNF1A subtype ✓

Explanation

Early onset, vertical transmission through three generations, absence of obesity and autoantibodies, preserved D-peptide, and lifelong ketosis resistance define MODY. HNF1A-MODY (formerly MODY3) is the commonest subtype worldwide and characteristically responds well to low-dose sulfonylureas. Type 1 and LADA require positive autoantibodies and progress to absolute insulin deficiency, while type 2 diabetes in this age group is almost always associated with obesity and insulin resistance.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.