Fulminant type 1 diabetes mellitus in a GDM pregnancy : early recognition is vital for maternal and fetal outcomes

Fulminant type 1 diabetes mellitus (FT1DM) is characterised by extremely rapid destruction of pancreatic beta cells. An association between FT1DM and pregnancy has been reported and can lead to unfavourable pregnancy outcomes without timely treatment. We report a case of FT1DM in a pregnancy with gestational diabetes mellitus (GDM), the first of its kind in the English literature to date. A 27-year-old woman with insulin-requiring GDM presented with rapidly deteriorating glycaemic control in her third trimester of pregnancy despite good concordance to treatment. The investigation identified the hallmarks of FT1DM: hyperglycaemia with acute metabolic decompensation and non-immune-mediated beta-cell failure. She received prompt treatment with intravenous insulin therapy and was transitioned to subcutaneous insulin once biochemical improvement had been achieved, albeit with higher insulin requirements than before. She had a good pregnancy outcome and delivered a healthy male infant 5 weeks later through induction of labour. Due to persistent beta-cell dysfunction, she remained on basal-bolus insulin postpartum. This case highlights the importance of early recognition and treatment of FT1DM in pregnancy to prevent adverse maternal and fetal prognoses.