What is the most likely cause of her diabetes?

A 33-year-old woman was seen for diabetes review 2 months after her first pregnancy. Diabetes mellitus had been diagnosed at 18 weeks’ gestation. She had experienced no symptoms; routine urinalysis had shown glucose 4+, with no ketones, and her fasting blood glucose concentration was 6.2 mmol/L (3.0C6.0), rising to 13.5 mmol/L (<7.8) in a 75-g oral glucose tolerance test. She had been treated with insulin during the pregnancy, and stopped after delivery. Her mother and maternal aunt had been treated for type 2 diabetes mellitus, and a maternal uncle for type 1 diabetes. Her body mass index was 23.7 kg/m2 (18C25).

Without insulin she remained well, with no osmotic symptoms, no weight loss and no ketosis.

Investigations:

fasting plasma glucose8.4 mmol/L (3.0C6.0)

haemoglobin A1c68 mmol/mol (20C42)

oral glucose tolerance test (75 g):

fasting plasma glucose7.9 mmol/L (3.0C6.0)

2-h plasma glucose13.8 mmol/L (<7.8)

serum insulin72 pmol/L (<186)

serum C-peptide945 pmol/L (180C360)

A trial of therapy with gliclazide 40 mg once daily led to a significant improvement in her blood glucose.

What is the most likely cause of her diabetes?
A . latent autoimmune diabetes in adulthood
B . maturity-onset diabetes of the young caused by glucokinase mutation
C . maturity-onset diabetes of the young caused by HNF-1? mutation
D . type 1 diabetes mellitus
E . type 2 diabetes mellitus

View Answer

Answer: C