Importance of clinical variables in the diagnosis of MODY2 and MODY3

MODY (maturity onset diabetes of the young) is a group of well-defined diseases clinically characterised by onset before age 25 years that does not require insulin treatment (at least initially) to prevent the formation of ketone bodies and autosomal dominant inheritance. Despite the importance of accurate classification, it is not always simple to catalogue the diagnosis of a young patient with diabetes, and genetic studies are often improperly used.

We describe the clinical features of patients negative for MODY2 and MODY3 and compared them to patients positive for these subtypes.

All patients with MODY3 had been diagnosed before age 25 years and required drug therapy for blood glucose control. MODY2 patients were diagnosed at the first laboratory workup either incidentally or as part of gestational diabetes screening. The clinical description of the 19 patients negative for MODY2 and MODY3 showed that only two patients presented a clinical picture consistent with MODY3 and one patient with MODY2.

Clinical features can be used for early exclusion of a MODY2 or MODY3 diagnosis and may reduce the need for genetic testing.