Transient abnormal myelopoesis in an infant with Down syndrome

A three-week-old boy with Down syndrome presented with poor feeding and jaundice. He had been born at term by normal delivery at home. The pregnancy had been uneventful and the mother had declined antenatal testing so the diagnosis of Down syndrome was made in the postnatal period. The infant required oxygen at birth and was admitted to the neonatal unit for a few days after birth. He started to become jaundiced after discharge. There was no family history of note and the infant has three siblings who are healthy. The mother is Rh D positive. On examination the infant was jaundiced, with neither hepatosplenomegaly, nor signs of sepsis but had hypotonia typical of Down syndrome. Investigations revealed unconjugated jaundice with a negative direct antiglobulin test. A full blood count showed thrombocytopenia with a platelet count of 65 10/L, a white cell count of 8.6 10/L, neutrophil count of 1.9 10/L and haemoglobin level of 18.0 g/dL. Blast cells of medium to large size with cytoplasmic blebs were found on the blood film (see Fig. 1). Immunophenotyping showed the blasts to have myeloid markers with expression of CD41 and CD61. The infant was treated with phototherapy and the jaundice improved. He was followed up closely with weekly full blood counts for two months.