Neonatal Platelet Disorders

Thrombocytopenia is, after anemia, the most frequent hematological problem among sick neonates. In this population, thrombocytopenia has traditionally been defined as a platelet count 9 /L, and has been classified as mild (100–150 × 10 9 /L), moderate (50–99 × 10 9 /L), and severe ( 9 /L). However, large population-based studies have shown that platelet counts increase with advancing gestational age, and platelet counts between 100 and 150 × 10 9 /L are more frequent among otherwise healthy extremely preterm infants than among full term neonates or older children. This suggests that different definitions of thrombocytopenia and thrombocytosis should be applied to preterm infants. The diagnostic approach to a thrombocytopenic neonate is facilitated if the thrombocytopenia is categorized as “early onset” (within the first 72 hours of life, usually secondary to congenital or intrauterine abnormalities) or “late onset” (after 72 hours, usually due to acquired conditions). Importantly, infection/sepsis should always be considered near the top of the differential diagnosis, as any delay in diagnosis and treatment can have life-threatening consequences. While in vitro studies have clearly shown that neonatal platelets are hyporesponsive to most agonists, this platelet hyporeactivity is well compensated by factors in neonatal blood that increase clotting (i.e. high hematocrit, high VWF concentrations), resulting in adequate primary hemostasis. The risk of bleeding in thrombocytopenic neonates is poorly predicted by the platelet count; gestational age