Although antenatal care and diagnosis have improved and many abnormalities are now anticipated infants are still born that pose diagnostic conundrums. We present one such scenario with complex diagnostic and management challenges.

Emily was born at 35⁺⁶ weeks. This was the first pregnancy for her 19-year-old mum who had no significant medical or obstetric history. She was known to fetal medicine because of fetal growth retardation, with an estimated fetal weight at 33⁺⁴ weeks below the third percentile. Following a 3-week period of static growth labour was induced for fetal wellbeing. Shortly after induction following fetal bradycardia Emily was delivered by caesarean section.

Emily weighed 1.58 kg (<0.4th centile) with a head circumference (OFC) of 28.5 cm (0.4th centile) and was admitted to the neonatal unit.

On arrival Emily was noted to be dusky, with nasal flaring and oxygen saturations of 40% in air.

She was commenced on continuous positive airway pressure (CPAP). Her temperature was 34.2°C, heart rate 140/min and systolic blood pressure (BP) 42 mm Hg. Emily had several petechiae on her trunk, face and legs; abdominal examination revealed marked hepatosplenomegaly. Neurological and cardiovascular examinations were normal. The registrar considered several differential diagnoses including congenital viral infection, alloimmune thrombocytopaenia and sepsis. Intravenous access was obtained, blood was sent for full blood count (FBC) and blood culture and intravenous benzylpenicillin and gentamicin were commenced.

The FBC revealed that Emily was thrombopcytopaenic: platelets 21×10⁹/l, haemoglobin 16.5 g/dl and white cell count 6×10⁹/l. Urea, electrolytes, liver function and clotting were also checked and found to be within normal range.

The registrar explained to parents that the examination findings and low platelet count required further investigation and that Emily required an urgent platelet transfusion.