A 17-year-old lean boy has fasting glucose 132 mg/dL and HbA1c 7.6%. His father and paternal aunt developed diabetes before age 25 and are not obese. Anti-GAD antibodies are negative, C-peptide is preserved, and he is not ketosis-prone. Which feature best supports maturity-onset diabetes of the young due to HNF1A mutation over type 2 or type 1 diabetes?
- A Autosomal dominant transmission across generations with onset before 25 years in non-obese, antibody-negative individuals ✓
- B Obesity with acanthosis nigricans and strong insulin resistance markers
- C Presence of diabetic ketoacidosis at presentation
- D Deafness and maternal-only transmission pattern
Correct answer: A. Autosomal dominant transmission across generations with onset before 25 years in non-obese, antibody-negative individuals
Explanation
MODY is characterised by autosomal dominant inheritance (three generations affected), onset typically before 25 years, absence of autoimmunity and obesity, and preserved C-peptide. HNF1B-MODY (MODY 3) is notably sulfonylurea-responsive. Option D describes maternally inherited diabetes and deafness from mitochondrial DNA mutation (MIDD), a different entity. Ketoacidosis points toward type 1 diabetes, and obesity with acanthosis supports type 2 diabetes, both of which argue against MODY.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.