MODY (Maturity-Onset Diabetes of the Young)

Key points

• MODY is a group of AUTOSOMAL DOMINANT monogenic diabetes syndromes causing beta-cell dysfunction — it is NOT a single gene. The commonest subtypes are HNF1A, GCK and HNF4A; HNF1B is a less common subtype.
• HNF1A (the commonest symptomatic MODY): progressive hyperglycaemia, low renal threshold for glucose, and marked SULFONYLUREA SENSITIVITY — these patients often come OFF insulin onto low-dose sulfonylurea, which is the classic exam point.
• GCK (glucokinase) MODY: mild, stable, non-progressive fasting hyperglycaemia present from birth, minimal complications — usually needs NO treatment outside pregnancy.
• HNF4A: similar to HNF1A and also sulfonylurea-sensitive · associated with macrosomia and neonatal hypoglycaemia.
• HNF1B (renal cysts and diabetes, RCAD): renal cysts, renal impairment, genital tract malformations, pancreatic atrophy and deranged liver function — these patients generally require INSULIN and are NOT sulfonylurea-responsive. Features of MODY
• typically develops in patients < 25 years
• a family history of early onset diabetes is often present
• ketosis is not a feature at presentation