A 17-year-old lean girl has 3 years of mild fasting hyperglycaemia without ketosis, a strong paternal history of early-onset diabetes, and negative anti-GAD antibodies. Her cousin with the same condition is well controlled on a low-dose sulfonylurea. Genetic testing shows an HNF1-alpha mutation. Which statement about her condition is correct?

• A Insulin therapy is required from diagnosis in all carriers
• B Sulfonylureas provide better glycaemic control than insulin in HNF1-alpha maturity-onset diabetes of the young ✓
• C She has a progressive autoimmune beta cell destruction process
• D Metformin is the agent of first choice because obesity drives her hyperglycaemia

Explanation

Maturity-onset diabetes of the young due to HNF1-alpha mutations is autosomal dominant, ketosis-resistant, antibody-negative, and characteristically shows a low renal threshold for glycosuria. Affected individuals retain functional beta cells that respond exceptionally well to sulfonylureas, which often achieve better control than insulin at equivalent doses, making them first-line. Autoimmune destruction defines type 1 diabetes, and obesity-related insulin resistance defines type 2, neither of which fits this monogenic phenotype.

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

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Written and medically reviewed by the StethoPrep medical team.