Hematology Basics and Blood Components

Hematology

• Hematology is the science that studies diseases related to blood and its components.
• Blood is a viscous fluid comprised of formed elements (cells) and a fluid component (plasma).
• The average adult has about 5 liters of blood, circulating throughout the circulatory system.

Blood Components

• Plasma (55%): The liquid part of blood, containing water, proteins, and other solutes.
• Formed elements (45%): Cells and cell fragments in blood. These include red blood cells (RBCs), white blood cells (WBCs), and platelets.

Normal Hematopoietic Differentiation

• Pluripotent stem cells differentiate into myeloid and lymphoid stem cells.
• Myeloid stem cells give rise to red blood cells, platelets, and various types of white blood cells (e.g., neutrophils, basophils, eosinophils, monocytes).
• Lymphoid stem cells give rise to lymphocytes (e.g., B cells, T cells, natural killer cells).

Red Blood Cell (RBC) Disorders

• RBC disorders can be classified as a result of abnormal RBC production, destruction, or loss.

Anemia

• Anemia is a condition where there's a reduction in the concentration of hemoglobin below the normal range for age and gender.
• This leads to reduced oxygen-carrying capacity of blood, causing tissue hypoxia.
• Low hemoglobin levels are different based on age and sex.
• Symptoms of anemia may vary depending on the severity, speed of onset, and age of the patient.

Diagnosis of Anemia

• Complete blood counts (CBC) include RBC count, hematocrit (Hct), and hemoglobin concentration.
• RBC indices (MCV, MCH, MCHC, RDW) are calculated from CBC results and used to classify anemia types, providing more detailed information about RBC size, hemoglobin content, and variation in size.
• Reticulocyte count indicates bone marrow activity. Lower reticulocyte counts may point to a problem with the bone marrow.

Classification of Anemia

• Inadequate production of RBCs by the bone marrow (e.g., iron deficiency, vitamin B12/folate deficiency, aplastic anemia).
• Excessive destruction of RBCs (hemolysis – e.g., sickle cell anemia, autoimmune hemolytic anemia).
• Blood loss (hemorrhage). -Further classification types exist for anemia including based on blood indices (e.g., hypochromic microcytic, macrocytic, and normochromic normocytic)

Hemoglobin Structure

• Hemoglobin is a protein found in red blood cells, responsible for oxygen transport in the body.
• Hemoglobin is composed of a heme group (containing iron) and globin chains.

Iron Deficiency Anemia

• Iron is an essential mineral for hemoglobin production.
• Iron deficiency anemia results from inadequate iron intake, absorption issues, or excessive losses.
• Characterized by a reduced amount of functional hemoglobin in the body.

Anemia of Chronic Disease

• Anemia that develops in the context of a chronic inflammatory or malignant condition can be referred to as anemia of chronic disease.
• It can be caused by reduced iron release from macrophages.
• Other causes include decreased erythropoietin production (a hormone important for red blood cell production), reduced red blood cell lifespan, and cytokine effects on erythropoiesis.

Hemoglobinopathies

• Genetic disorders affecting hemoglobin structure.
• Thalassemia: Reduced synthesis of globin chains, resulting in ineffective erythropoiesis.
• Sickle cell disease: Abnormal globin chains resulting in rigid, sickle-shaped erythrocytes.

Alpha Thalassemia

• Group of genetic disorders characterized by reduced or absent alpha-globin production, leading to variations in severity.

Beta Thalassemia

• Group of inherited conditions resulting from reduced Beta-globin production, causing varying degrees of anemia.

Clinical Findings/features

• General and specific findings related to anemia of varying types
• Physical findings related to anemia