Frequency and genetic spectrum of maturity-onset diabetes of the young (MODY) in southern New Zealand

Abstract

Maturity-Onset Diabetes of the Young (MODY) is a monogenic form of diabetes, consisting of a heterogeneous group of autosomal dominant inherited disorders. Typical onset is in individuals prior to twenty five years, and presentation can mimic type 1 or 2 diabetes. Molecular genetic testing can allow precise identification of the different MODY sub-types. Making a specific diagnosis of MODY can have important implications for the guidance of appropriate treatment, prognosis and genetic counselling.We present the cases of three children and their families diagnosed with MODY over the past two years. These families highlight the features of three of the more common MODY subtypes, including two with novel mutations, one of which segregates in a kindred that is strongly affected by both MODY and classic autoimmune mediated diabetes. To date, we have identified a prevalence of MODY in the paediatric diabetes population of the lower South Island, New Zealand, of approximately 2.5%. This prevalence, along with increasing access to molecular genetic testing, highlights the importance of consideration of MODY in atypical diabetes presentations in the paediatric/adolescent population.

Figure 1

Typical BGLs on continuous glucose monitoring - case 1.

Figure 2

One copy of the variant c.698G>A (p.Cys233Tyr) in exon 7 of the GCK gene (Refseq accession number NM_000162).

Figure 3

Family tree - case 1.

Figure 4

Case 2 - Family tree.

Figure 5

Case 3 – family tree.

Figure 6

Frameshift mutation c.864delGinsCC, or c.864G>C and c.872dupC, (p.Gly292ArgfsX25) in exon 4 of the HNF1α gene (Refseq accession number NM_000545).