Table 1.

Comparison of main types of monogenic diabetes with type 1 and type 2 diabetes

Feature	HNF1A-/4A-MODY	HNF1B-MODY	GCK-MODY	T1DM	T2DM
Typical age at diagnosis	10–45 years	10–45 years	Birth onwards	1–30 years	After 25 years
Ketonaemia/diabetic ketoacidosis	Very rare	Very rare	Would not be predicted to occur	Common	Rare except in ketosis-prone subtype
First-degree relative with DM	Reported in 50–60%	Around 50% (high rate of spontaneous mutations)	Often undiagnosed or reported as IGT/GDM	2–4%	Around 50%
Insulin resistance/obesity	Same as non-diabetic population	Same as non-diabetic population	Same as non-diabetic population	Same as non-diabetic population	Common
Beta-cell antibodies	Negative	Negative	Negative	Positive at diagnosis in 80–90%	Negative
C-peptide after 3 years from diagnosis	Normal range	Normal range	Normal range	Low or undetectable in majority	High normal
First-line drug treatment	Low-dose sulphonylurea	Metformin if renal function allows	None	Insulin	Metformin

DM = diabetes mellitus. GCK = glucokinase. GDM = gestational diabetes mellitus. IGT = impaired glucose tolerance. MODY = maturity-onset diabetes of the young. T1DM = type 1 mellitus. T2DM = type 2 diabetes mellitus.