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Disorders of Erythrocytes
- Iron deficiency anemia is the most common blood disorder of infancy and childhood; the highest incidence occurs between 6 months and 2 years of age.
- Hemolytic disease of the newborn (HDN) results from incompatibility between the maternal and the fetal blood, which may involve differences in Rh factors or blood type (ABO). Maternal antibodies enter the fetal circulation and cause hemolysis of fetal erythrocytes. Because the immature liver is unable to conjugate and excrete the excess bilirubin that results from the hemolysis, icterus neonatorum or Kernicterus or both can develop. Kernicterus, which also may result from other causes, causes increased breakdown of red blood cells or decreased liver output of enzymes.
- Infections of the newborn, often acquired by the mother and transmitted to the infant, may result in hemolytic anemia.
- Sickle cell disease is a genetically determined defect of hemoglobin synthesis inherited by an autosomal recessive transmission; it causes a change in the shape of a red blood cell that results in decreased oxygen or hydration. It is most common among Africans and those of Mediterranean descent.
Disorders of Coagulation and Platelets
- Hemophilia is a condition characterized by impairment of the coagulation of blood and a subsequent tendency to bleed. The classic disease is hereditary and limited to males, being transmitted through the female to the second generation. Many similar conditions attributable to the absence of various clotting factors are now recognized.
- The acquired antibody-mediated hemorrhagic diseases include idiopathic thrombocytopenic purpura (ITP), transient neonatal thrombocytopenia, and autoimmune vascular purpura.
- ITP, the most common of the childhood thrombocytopenic purpuras, is a disorder of platelet consumption in which antiplatelet antibodies bind to the plasma membranes of platelets. This results in platelet sequestration and destruction by mononuclear phagocytes at a rate that exceeds the ability of the bone marrow to produce them.
- The childhood leukemias include, in order of their rate of incidence, acute lymphoblastic, acute myeloblastic, and the very rare chronic myelocytic leukemia.
- Although the cause of childhood leukemia is not known for certain, it is probably the result of multiple interactions between hereditary or genetic predisposition and environmental influences.
- Acute lymphoblastic leukemia is a potentially curable disease, with about 80% of cases cured.
- The lymphomas of childhood are Hodgkin lymphoma and non-Hodgkin lymphoma.
- The origin of non-Hodgkin lymphoma is unknown. Factors that have been implicated include defective host immunity, a viral agent, chronic immunostimulation, and genetic predisposition.
- Non-Hodgkin lymphoma had a favorable prognosis, with a 60% to 80% rate of cure.
- Hodgkin lymphoma is thought to be caused by a yet unidentified etiologic agent.
- Hodkin lymphoma in children is a readily curable disease with survival statistics similar to those for adults.