Newborn platelet disorders
Bizzozero is credited with the first description of platelets, the last blood cell to be described . Similarly, the understanding of platelet formation has lagged behind the study and understanding of erythropoiesis and myelopoiesis. The isolation of thrombopoietin in 1994 [2–6], the development of better techniques to isolate megakaryocytes [7–17], and the advent of molecular biology have brought about a much better understanding of megakaryocytopoiesis/thrombopoiesis, as well as the final steps of platelet production and release. Yet, our understanding of newborn platelets is incomplete. In this chapter, we will discuss briefly the ontogeny of hematopoiesis, megakaryocytopoiesis, thrombopoiesis, and platelet production, concentrating on the differences between adult and fetal processes. The majority of the chapter is devoted to platelet disorders of the newborn.
Megakaryocytopoiesis and thrombopoiesis in the newborn
Our current understanding of hematopoiesis is based on the hypothesis that there is a hematopoietic stem cell capable of differentiating into all hematopoietic cell lines, including megakaryocyte/platelet lineage [18–22]. Hematopoietic stem-cell-transplantation animal models and cell-culture techniques, developed in the 1960s and 1970s, documented the ability of bone-marrow cells to reconstitute all hematopoietic lineages, which proved the existence of this hematopoietic progenitor cell . For instance, Till and McCulloch in 1961  documented that hematopoietic stem cells could reconstitute the blood in animals given otherwise lethal doses of radiation. Lineage-specific in vitro assays for myeloid, erythroid, megakaryocytic, and multilineage progenitor cells were first developed in mice [23–26] and now are available for human progenitors [27–30].