Anemia: Decrease in the oxygen-carrying capacity of the blood; indicated by a low red blood cell count and hemoglobin concentration.

Anomaly: Deviation from what is regarded as normal; congenital malformation.

Apoptosis: The mechanism by which cells are systematically eliminated from the body.

Bone Marrow: Soft tissue within the bones; where blood cells are manufactured.

Bone Marrow Aspiration: Test in which a sample of bone marrow cells is removed with a needle and examined under a microscope.

Bone Marrow Transplant: Procedure during which bone marrow stem cells of the patient are destroyed by chemotherapy and/or radiation and then replaced with healthy stem cells from a donor. Stem cells may also be obtained from peripheral blood or umbilical cord blood.

Chelation: A system to remove excess iron from the blood and tissues.

Chronic: Of long duration; designating a disease showing little change, or, of slow progression.

Complete Blood Count (CBC): A test that checks the number of red blood cells, white blood cells, and platelets in a sample of blood.

Congenital: Present at birth.

Cytokines: Growth factors which promote the proliferation and maturation of blood cells.

Diamond Blackfan Anemia: A rare pure red blood cell anemia of infancy and childhood resulting from the failure of the bone marrow to produce red blood cells.

Differential: Percent of different types of white blood cells in the blood.

Dominant: In genetics, a trait or characteristic that will be expressed in the offspring even though it is carried on only one of the homologous (parental) chromosomes.

Endocrine: System to secrete; the network of ductless glands and other structures that elaborate and secrete hormones directly into the blood stream, affecting the function of specific target organs.

Erythropoietin: Hormone produced in the kidneys which drives red blood cell production.

Etiology: The cause of a disease.

Granulocyte: Type of white blood cell; includes the basophil, eosinophil, and neutrophil (or poly), which is the infection-fighting cell.

Hematology: Study of the blood.

Hematocrit: Ratio of red blood cells to plasma in the blood; portion of the blood’s total volume that is made up of red blood cells. Normal values vary: men 45% to 57%; women 37% to 47%; children depending on age 36% to 40%.

Hemoglobin: Hgb or Hb; iron-containing coloring in the blood cells that combines with oxygen from the lungs and carries it to the body’s cells. Normal values for men: 14 to 18 g/dl: women 12 to 16 g/dl; children 12 to 16 g/dl.

Hematopoiesis: The forming of new blood cells.

Hypoplastic: Defective formation; incomplete development of a part.

Leukocyte: A white blood cell formed in lymphoid tissue throughout the body, e.g., lymph nodes, spleen, thymus, tonsils, and sometimes in bone marrow.

Megakaryocyte: Large cells in the bone marrow from which pieces break off to form platelets.

Multipotent: Having the ability to become more than one cell type

Neutropenia: Low neutrophil (poly) count.

Neutrophil: Type of white blood cell; also call granulocyte or polymorphonuclear leukocyte (poly). Normal values are 50-60 percent or 3,000 to 7,000 in number.

Osteoporosis: Loss of bone calcareous matter and increased bone porosity.

Pancytopenia: Low number of all blood cells.

Parvovirus B-19: The cause of a usually benign disease known as fifth disease; in immunocomprised patients, may cause aplastic anemia.

Platelets: Blood cells which form clots therefore preventing bleeding and bruising. Normal values range from 150,000 to 400,000 per microliter of blood. A count below 50,000 can result in spontaneous bleeding; below 5,000 patients are at risk of severe life-threatening bleeds.

Precursors: A substance that precedes another substance.

Progenitor: A parent or ancestor; anything that originates or precedes. Blood cell progenitors are derived from stem cells an give rise to precursors

Red Blood Cell: Oxygen-carrying cell in the blood which contains the pigment hemoglobin, produced in the bone marrow; erythrocyte. Counts refer to the number of cells in a single drop (microliter) of blood. Normal ranges vary according to sex and age.

Refractory: Not responding to treatment

Reticulocyte (Retic) Count: Number of young red blood cells.

Stem Cell: Cell from which platelets, red blood cells, and white cells grow in the bone marrow.

Thrombocyte: Platelet; clotting factor in the blood.

Thrombocytopenia: Low platelet count.

White Blood Cells: Blood cells which fight infection. Normal values range from 4,100 to 10,900 cells in a microliter of blood (drop) but can be greatly altered by factors such as stress, exercise and disease.