Case 2: Dropping platelet counts in the neonatal intensive care unit - An unsuspected cause for thrombocytopenia in a neonate

A premature baby girl born at 28 weeks’ gestation developed thrombocytopenia at approximately 50 days of life (corrected gestational age >35 weeks), which was noted on routine blood work during her admission to the neonatal intensive care unit (NICU). The mother’s pregnancy history was significant for limited pre-natal care. Routine serological testing for rubella, varicella, syphilis, hepatitis B and HIV was not performed, although HIV and hepatitis testing had been normal two years previously. Group B streptococcus status was negative. There was no history of maternal thrombocytopenia. The baby was born at 28 weeks’ gestation via spontaneous vaginal delivery at a peripheral hospital. The infant’s birth weight was 935 g. She was intubated at delivery for low Apgar scores, and transferred to a tertiary care institution for ongoing care. Ongoing neonatal issues at the time of presentation included a persistent oxygen requirement, apnea and bradycardia of prematurity, and poor growth despite fortified feeds. There were intermittent stools positive for occult blood, but no x-ray evidence of necrotizing enterocolitis or feed intolerance. The patient’s complete blood count had been normal at birth, one week of life and four weeks of life. However, the subsequent test at two months of life revealed normocytic anemia and moderate thromobocytopenia. Given the new finding, empirical treatment with broad-spectrum intravenous antibiotics was started for presumed infection. Platelet transfusion was given with an appropriate, albeit transient rise in platelet count. Physical examination was remarkable for mild pallor and palpable cervical lymph nodes in an otherwise well-appearing, nondysmorphic, but small-for-corrected gestational age newborn. Investigations including a complete blood count showed normocytic anemia (hemoglobin level 78 g/L); normal white blood cell count with atypical lymphocytes; and a platelet count of 15×109/L. Platelet reticulocytes were elevated. Liver enzyme levels were mildly elevated, with aspartate aminotransferase 109 U/L and alanine aminotransferase 45 U/L. Echocardiogram and head, abdominal and extremity ultrasounds were unremarkable, with no evidence of thrombus, acute hemorrhage or splenomegaly. Initial infectious work-up, including blood and urine cultures; Epstein-Barr virus serology; urine cytomegalovirus; and hepatitis A, B and C screen, were negative. Rubella serology was indeterminate. An additional blood test confirmed the diagnosis.