A female infant (weight 2700g (small for gestational age, SGA), length 47 cm, occipitofrontal circumference (OFC) 32 cm) was born at 38+6 weeks to a 33-year-old G1/P1 by elective caesarean section. There was no maternal history of unexplained primary sterility, spontaneous abortions or peri/neonatal deaths as well as no maternal health issues during pregnancy and no suggestion of maternal diabetes mellitus or gestational diabetes. Postnatal adaptation was normal with APGAR scores of 9, 10 and 10 after 1, 5 and 10 min, respectively. Early medical examination did not reveal any abnormalities. On the first day of life, the infant showed hypoglycaemia with blood glucose values between 1.7–2.2 mmol/l despite early feeding with maltodextrine. Blood glucose values normalised on an intravenous glucose infusion. During the following days ongoing intravenous glucose administration was necessary despite increased oral feeding. The initial metabolic workup included cortisol, insulin, growth hormone, lactate and ammonia. These bloods were sampled at a glucose concentration of 2.7 mmol/l. The results were normal other than a slight hyperammonaemia at 141 μmol/l (controlled 159 μmol/l). A screen for inborn errors of metabolism showed no distinctive features.
With a presumed diagnosis of prolonged transient hyperinsulinism secondary to growth restriction we began treatment with hydrocortisone (2 mg twice daily), which stabilised blood glucose values with normal feeding.
At the age of 8 weeks hydrocortisone medication was terminated. Blood glucose values remained within the normal range, ammonia was slightly elevated at 92 μmol/l.
The infant was readmitted at the age of 5½ months for observation after a fall to the floor from a “babysafe” carry system. Clinical examination was inconspicuous. Sensorimotor development as well as growth was normal for its age. No neurological symptoms appeared until discharge 2 days later.
Three hours after returning back home, an episode of abnormal jerky movements of the head with an empty gaze was observed over a period of 5 min. Feeding had been normal that morning with 180–200 ml formula milk every 4–5 h plus a half portion of porridge. On admission to hospital, the blood glucose concentration was measured at 2.2 mmol/l. A computed tomography (CT) scan of the skull excluded acute intracranial haemorrhage and the electroencephalogram (EEG) recordings showed no pathologic activity. Intensified metabolic workup showed the following results.