Non-Malignant Blood Disorders in Adolescence

IntroductionThe public health impact of various forms of cytopenias, anemias, bleeding and clotting disorders, and hemoglobinopathies is enormous and recognition is important not only for prevention of complications, but also for treatments to improve quality of life. Early recognition also provides an opportunity to address preconception care during adolescence and education. Management often requires comprehensive care that includes plans for transition of care to adults, especially in those disorders that are inherited.AnemiaAnemia is the most common hematologic problem seen in adolescence. The physiologic definition of anemia is a decrease in oxygen carrying capacity of the blood. However, for all practical purposes anemia is defined as hemoglobin values two standard deviations below the mean. As the child matures and attains Tanner 4 maturation the red cell volume and the red cell mass reaches adult normal values (1). In addition to Tanner stage, the hemoglobin values are also affected by race, gender, hereditary factors and altitude (2). Hemoglobin values are lower in females (normal range 11.2-13.6g/dl) than males (normal range 11.5-14.8g/dl) and are also lower in African Americans than Caucasians.The normal values are procedure dependent. Consult with a lab for the normal value. Adolescents with chronic hypoxic cardiopulmonary conditions have higher hemoglobin and show symptoms of anemia at a higher hemoglobin level.Mechanism of anemiaErythropoiesis is a very tightly regulated process. Erythropoietin, one of the red cell growth factors, is produced by the kidney and plays a critical role in proliferation and maturation of red cells. Under physiologic conditions red cells endowed with hemoglobin are released in the circulation as reticulocyte. Reticulocytes take one day in the peripheral circulation to mature to RBC.Normal life span of a mature RBC is 120 days. Senescent red cells are removed from the circulation by reticuloendothelial cells in the spleen and other organs. A delicate balance between red cell production and normal senescence maintains normal hemoglobin and oxygen delivery. Normal hematopoietic progenitors have tremendous ability to compensate for loss of red cells, provided there is an adequate supply of nutrients such as iron, B12 and folic acid.Failure of the bone marrow to respond to blood loss, either due to normal senescence or other pathologic processes, results in an imbalance that leads to anemia (3). The reticulocyte count is a good measure of red cell kinetics, the bone marrow's ability to produce red cells. Most routine laboratories use a hematology analyzer and report absolute reticulocyte count. Anemia associated with an increase in absolute reticulocyte count is the result of increased red cell destruction; whereas low or normal reticulocyte count in a patient with anemia is suggestive of decreased red cell production. A comprehensive classification of anemia (Table 1) uses this red cell kinetics. Reticulocyte count is not part of a routine CBC. Most laboratories will do reticulocyte count on the blood drawn for a CBC if the test is requested within the first 24 hours of blood draw. Red cell indices such as mean corpuscular volume (MCV), mean corpuscular hemoglobin concentration (MCHC) and red cell distribution width (RDW) are part of a complete blood count (CBC) and are used to classify anemia based on MCV (Table 2). Although classification of anemia based on red cell kinetics provides a better understanding of the underlying process, the classification based on red cell indices is easier to apply in a clinical setting. Review of peripheral smear provides very useful information regarding red cell morphology and may help establish the diagnosis. Peripheral smear is not a part of routine CBC. Indications for peripheral smear are listed in Table 3. In cases of normocytic anemia with low reticulocyte count or macrocytic anemia, a bone marrow evaluation is required to establish the diagnosis. …