Aim To highlight the presentation and treatment of Hyperglycaemic Hyperosmolar Syndrome (HHS) presenting atypically in a paediatric diabetic patient.

Case history A previously well 5-year-old boy presented to his local hospital with loss of consciousness. He had a 10 day history of weight loss, polydipsia, polyuria and secondary nocturnal enuresis. He had been drinking large volumes of high sugar content juice. He also had 3 days of abdominal pain and multiple bouts of emesis on the day of presentation. He was found to be lethargic and was immediately transported to hospital. At the emergency department, he was minimally responsive (GCS = 3) and hypopnoeic. He was intubated and transferred to the ICU.

Initial blood glucose was 111 mmol/L. Venous Gas: PH 7.19, pCO243 mmHg, HCO3 15mmol/L, Lactate 3.8mmol/L. Serum Osmolality 381mosm/L. Na 135mmol/L, K 3.8mmol/L, Cl 95mmol/L, Creatinine 446mmol/L, Urea 22.5mmol/L, CPK 7351mmol/L. Urine ketones and serum toxicology screens were negative.

ICU course was notable for severe dehydration requiring copious fluid replacement. Hypotension required multiple inotropes. Hyperthermia requiring ice cooling developed; dantrolene was considered but not used. He had rhabdomyolysis and seizures. MRI showed abnormal FLAIR signal in the sub-cortical white matter of both occipital lobes. His hospital stay was complicated by left leg occlusive thrombus due to a femoral venous catheter. He needed physiotherapy to regain independent mobility.

Islet cell, anti-GAD and Insulin antibodies were positive, confirming Type I diabetes. C-peptide levels are pending.

Conclusion We present this case to highlight HHS as an unusual presentation and complication of Type 1 diabetes. The typical patient with HHS is an adult with established diabetes or an obese teenager of African descent. Our patient though black, did not fit this typical profile. HHS occurs less commonly than diabetic ketoacidosis in childhood diabetes although presenting features often overlap. Its management requires large fluid volumes to correct dehydration compared to fluid restriction in DKA. HHS is associated with greater mortality than DKA therefore, paediatricians need a high index of suspicion to diagnose and manage it effectively.