Pediatric hematology

Anatomy or system affected: Blood, bones, circulatory system, immune system, liver, musculoskeletal system, spleen

Definition: The diagnosis and treatment of blood disorders in infants and children

Science and Profession

Blood, the body’s life-sustaining fluid, is composed of red and white cells and platelets floating in plasma. Blood transports oxygen from the lungs to the tissues; removes waste products such as carbon dioxide, urea, and lactic acid; transports hormones and nutrients; moves body heat from central to peripheral parts of the body; clots in order to seal hemorrhages; transports leukocytes and antibodies to fight injury and infection; and stores and circulates elements such as calcium and iron. The diagnosis of hematologic disorders requires the comparison of blood and bone marrow values to established reference ranges. These ranges can vary considerably during a child’s growing years, with such important changes as polycythemia in the neonatal period followed by physiologic anemia of infancy, which is maximal at two and a half to three months.

Pediatric hematology involves the ongoing assessment of an infant’s or child’s blood and bone marrow. Routine blood screenings, in which blood is removed by a medical laboratory phlebotomist using venipuncture in children and heel or finger stick in infants, are performed to establish a complete coronary risk profile with lipid fractionation, a complete blood count (CBC), a chemistry 27 profile, an iron-deficiency profile, and diabetes mellitus screening.

A complete coronary risk profile with lipid fractionation is an assessment of total serum cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, very low-density lipoprotein cholesterol, total cholesterol/high-density lipoprotein cholesterol ratio, triglycerides, chylomicrons, and possibly apolipoproteins. A CBC includes analysis of hemoglobin, hematocrit, and red and white blood cell counts with white blood cell differential, including granulocytes (neutrophils, eosinophils, and basophils) and agranulocytes (lymphocytes and monocytes). A chemistry 27 profile assesses important blood constituents such as iron and protein storage, uric acid, several electrolytes, and enzymes. An iron-deficiency profile includes measurements of total iron-binding capacity, percentage of transferrin saturation, and serum ferritin. Diabetes mellitus screening, an assessment of glucose and protein-bound glucose (indicative of the previous seven to fifteen days), is important because only an estimated one-half of all diabetics are diagnosed.

Some of the major manifestations of hematologic disease in infants and children are disorders in the function of red blood cells, white blood cells, or hemostasis. Red blood cell disorders include anemia caused by the inadequate production of erythrocytes or hemoglobin as a result of genetic disease or iron deficiency, anemia caused by excessive loss of erythrocytes as a result of hemorrhage or hemolytic problems, polycythemia, erythrocytosis, erythremia, and blood transfusion. Disorders of white blood cells include leukopenia, agranulocytosis, periodic neutropenia, Chediak-Higashi syndrome, and leukemias. Blood diseases associated with defects in hemostasis include disturbances in the mechanism for clotting—such as hemophilia, von Willebrand disease, factor II (prothrombin) deficiency, factor XII deficiency, and disorders involving fibrinogen and fibrin—and defects in hemostasis in small vessels, such as thrombocytopenia, Wiskott-Aldrich syndrome, and thrombopoietin deficiency.

Diagnostic and Treatment Techniques

The diagnosis of pediatric hematological disorders begins with a routine blood chemistry analysis, leading to more specific tests and a medical history of the infant or child and family members to determine if the problem is congenital or acquired, chronic or episodic, and static or progressive. Iron deficiency, also called anemia, is probably the most common nutritional problem in the world today. Anemia decreases work capacity by restricting oxygen and carbon dioxide transport and reducing aerobic energy production via the inhibition of iron-dependent muscle enzymes. Therapy for anemia generally involves diet manipulation and medication but is highly variable and depends on the specific causative factors. Since the prevalence of anemia correlates strongly with socioeconomic status, screening intervals and therapy must be planned individually for each child. Up to 20 percent of children from poor homes may be anemic at one year of age, while only 4 percent of children from higher-income homes will be anemic at the same age. Anemia becomes less common between three and five years of age, thus diminishing the need for regular screening.

Perspective and Prospects

Future research in pediatric hematology will probably include further investigation of reticulocytes, immature red blood cells that are larger than mature erythrocytes but nonnucleated and circulate in the blood for one to two days while maturing. Research into the causes and prevention of the development of anemia will continue to be a major focus.

Many countries, including the United States and Canada, require screening of all newborns for a variety of hereditary and infectious diseases. The first disease to be routinely screened for in newborns was phenylketonuria (PKU), a metabolic condition that can be toxic to brain tissue if not discovered early. Newborn screening is able to detect potentially life-threatening diseases long before the child starts to show symptoms.

Bibliography

American Society of Pediatric Hematology/Oncology. www.aspho.org

Eads, Jennifer R., Neal J. Meropol, and Jerry L. Spivak. "Update in Hematology and Oncology: Evidence Published in 2012." Annals of Internal Medicine, vol. 158, no. 10, May 2013, pp. 755–760.

Greer, John, et al., eds. Wintrobe’s Clinical Hematology. 15th ed., Wolters Kluwer/Lippincott Williams & Wilkins Health, 2024.

Hoffman, Ronald, et al., eds. Hematology: Basic Principles and Practice. 8th ed., Saunders/Elsevier, 2023.

Judd, Sandra J., ed. Childhood Diseases and Disorders Sourcebook. 2nd ed., Omnigraphics, 2009.

Keene, Nancy. Childhood Leukemia: A Guide for Families, Friends, and Caregivers. 5th ed., O’Reilly, 2018.

Miller, Denis R., Robert L. Baehner, and Linda Patricia Miller, eds. Blood Diseases of Infancy and Childhood: In the Tradition of C. H. Smith. 7th ed. Mosby Year Book, 1995.

Orkin, Stuart H., et al., eds. Nathan and Oski’s Hematology of Infancy and Childhood. 8th ed., Saunders/Elsevier, 2015.