Pathology Chapter 9 (Lesson 2) PDF

# Red Blood Cells ## Red Blood Cell Basics ### Blood Amounts - Men: 12 pints - Women: 9 pints ### Blood Function Carries oxygen, nutrients, platelets, and cells of the immune system. Removes waste. ### Blood Layers - Plasma (52-62%) - White Blood Cells and Platelets (<2%) - Red Blood Cells (38-...

# Red Blood Cells ## Red Blood Cell Basics ### Blood Amounts - Men: 12 pints - Women: 9 pints ### Blood Function Carries oxygen, nutrients, platelets, and cells of the immune system. Removes waste. ### Blood Layers - Plasma (52-62%) - White Blood Cells and Platelets (<2%) - Red Blood Cells (38-48%) ### Plasma - Solvent that suspends components of blood for absorption of molecules and their transport. - Transports thermal energy. - 90% water - With sugar, protein, fat, and salt. - 7% protein - With a specific function. - Make colloid osmotic pressure. - Ex: albumin, globulins (immunoglobulins), fibrinogen. - Others: electrolytes, nutrients, gasses (O2, CO2, N2), regulatory substances (enzymes & hormones), waste products (urea, uric acid) ### Hematopoiesis - Production of blood cells. - Starts in embryonic development in the yolk sac. - Taken over by liver and lymphatic organs. - Red bone marrow (adults). **Precursor of new blood cells is a pool of undifferentiated pluripotential stem cells.** ## Erythrocytes ### Appearance - Deformable. - Non-nucleated. - Biconcave disks. - Large surface area for oxygen diffusion. ### Function - Transports O2 from lungs to body and CO2from body to lungs. ### Other Important Facts - Most abundant blood cell. - Hematocrit is the packed RBC after it has been centrifuged. - Oxygen carrying cell (rich in hemoglobin). ### Hemoglobin - Iron-containing biomolecule. - Complex metalloprotein. - Releases O2 and carries waste. - Gives red color of the cells. - Mature erythrocyte has no nuclear material. - Embryonic liver is the primary location of production, influenced by the hormone erythropoietin (produced by the kidney). - RBC live for 100-120 days and are removed from circulation at the end. - Under a microscope, they appear as uniform round cells with central pallor (concavity). ## Variation in RBC ### Anisocytosis - Variation in the size of RBC. ### Nomocytic RBC - Normal size. ### Macroptosis - Larger RBC (elevated MCV). ### Microcytosis - Smaller RBC (decreased MCV). ### Mean Corpuscular Volume (MCV) - Measure of average volume or size of RBC. ## Erythropoiesis - Formation and life cycle of RBC. - Production of RBC takes 7 days. ## RBC Count - Counts the number of circulating RBC in 1 mm3 of peripheral venous blood. ### Anemic Value - Decreased below the expected value range. ### Decreased RBCs can be caused by: - Hemorrhage. - Hemolysis. - Dietary deficiencies. - Genetic aberrations. - Drug ingestion. - Marrow failure. - Bone diseases. ### Increased RBCs can be caused by: - Body needs for more oxygen carrying. - Diseases that produce hypoxia. ### Polycythemia Vera - A neoplastic condition causing uncontrolled production of RBCs. ### Drugs that increase RBC Count - Erythropoietin. - Gentamicin. ### Drugs that decrease RBC count - Decrease marrow production. - Cause hemolysis. ### RBC Collection and Testing - Blood is collected in EDTA tubes and inverted 7 times after collection to mix blood and anticoagulant. - RBCs release ATP when they are stress in constricted blood vessels and the ATP dilutes the RBCs. ## Polychromatic Erythrocyte - 3rd stage of erythropoiesis where cell division ceases. - Rounded nucleus with mature chromatin and no nucleoli. - Cytoplasm has hemoglobin synthesis. - Purple due to residual RNA. ## Reticulocyte Count - Increased bone marrow release of RBC in response to anemia. - Index should be 1.0. - **When elevated it is noticeable in the Wright Stain peripheral blood smear.** - Intermediate position between nucleated RBC and mature RBC. - Large, polychromatic RBC. ## Shift / Stress Reticulocyte - Shifted to circulation earlier than 2-3 days of maturity. - Has residual RNA. ## Abnormal RBC Morphology ## Blood cell Count & Normal Ranges | RBC x 10⁶/uL | RBC x 10¹²/L | | :---------------------------- | :---------------------------- | | **Adult/elder:** M:4.7-6.1 | **Adult/elder:** F: 4.2-5.4 | | **Children 2-8 week:** 1.0-6.0 | **2-6 months:** 3.5-5.5 | | **6 months-1 year:** 3.5-5.2 | **1-6 years:** 4.0-5.5 | | **6-18 years:** 4.0-5.5 | **Newborns:** 4.8-7.1 | ## What Prevents a Normal Count of Blood? - Improper anticoagulant. - Hemodilution. - Hemoconcentration. - High WBC count. - Abnormal shape RBC - Hemolysis. ## Hematocrit - **Indirect measurement of RBC # and volume.** - Mainly used for patients with bleeding, anemia, or who need rapid treatment. - Measures the percentage of total blood volume made up by RBC. - Measures the height of the RBC column that is centrifuged and compared to the column of total whole blood, then the ratio is multiplied by 100. - Affected by: - Abnormal RBC size (larger = higher HCT). - Hemodilution. - Dehydration. - Pregnancy (decreased). - High altitude (increased). ## Hemoglobin (Hgb) - Measure of Hgb in peripheral blood. - Determines the ability of blood to carry O2. ### Hemoglobin Normal Range | Gender | Normal Range | | :--------------------: | :---------------: | | **Adults** | M:14-18 g/dL | | | F: 12-16 g/dL | | **Pregnancy F** | >11 g/dL | | **Newborns** | 14-24 g/dL | | **0-2 weeks** | 12-20 g/dL | | **2-6 months** | 10-17 g/dL | | **6 months-1 year** | 9.5-14 g/dL | | **1 year - 6 years** | 9.5-14 g/dL | | **6 - 18 years** | 10-15 g/dL | | **Elderly** | Decreased Values | **Pregnancy** - Decreased Hgb levels can be caused by the dilution effect of expanded blood volume. - Slight diurnal variation in Hgb is expected. **High Altitude** - Increased Hgb levels occur because less O2 is available. ## Hemoglobin Synthesis - 2 pairs of globulin chains form a tetramer with a heme compound at each chain. **Newborn Hgb:** - 2 alpha globins and 2 gamma globins (higher affinity for O2). - At 12 months, gamma is replaced by delta and forms HgbA. **Hgb A:** - 2 alpha globin chains with 2 beta globin chains. - Makes up most Hgb. **HgbA2 and HgbF:** - Made of a pair of alpha and a pair of delta chains. - Make up the remaining Hgb. ## Breaking Down Hemoglobin - Removed by macrophages in the spleen and liver. - Broken into: - **Heme:** Iron is conserved and reused for more Hgb. - During metabolism, heme is converted to bilirubin, which is taken to the liver by albumin, to make bile. - **Globin:** Protein recycled or broken for amino acids. ## Mean Corpuscular Volume (MCV) - Measures the average volume/size of RBC and classifies anemias. - **MCV = Hematocrit (g/dL) x 10 / RBC (million/mm³)** - Adult/Elder/Child: 80-95fL - Newborn: 96-108 fL ## Mean Corpuscular Hemoglobin (MCH) - Measures the average amount of hemoglobin in RBC. - **MCH = Hemoglobin (g/dL) x 10 / RBC (million/mm³)** - Adult/elder/child: 27-31 pg - Newborn: 32-34 pg ## Mean Corpuscular Hemoglobin Concentration (MCHC) - Measure of average hemoglobin concentration or the percentage of hemoglobin in RBC. - **MCHC = Hemoglobin (g/dL) x 100 / Hematocrit (%)** - Hypochromic: Deficiency of hemoglobin (decreased MCHC). - Normochromic: Normal MCHC. - Cannot be hyperchromic since the maximum value is 37 g/dL. - Adult/Elder/Child: 32-36 g/dL (32%-36%) - Newborn: 32-33 g/dL (32%-33%) ## Red Blood Cell Distribution Width (RDW) - Indicates variation in RBC size. - Calculated using MCV and RBC values. - Anisocytosis: Blood condition where RBC have abnormal size. - Adult: 11.9%-14.5% ## Anemia - A state of RBC deficiency that lowers the ability to carry O2. - Classified by size (MCV) and hemoglobin (MCH) of RBC. - **Decreased hemoglobin and hematocrit.** - Causes: Blood loss. Hemolysis. Decrease RBC production. - **Hemolysis:** RBC destruction. **Hemolysis Symptoms:** - Pallor. - Fatigue. - Dyspnea. - Poor O2 - Chest pain - AMS **Body response:** - **Tachypnea:** Trying to make more gas exchanges. - **Tachycardia:** Circulating more volume. ### Causes of Hemolysis - **Intravascular Hemolysis:** - Mechanical RBC trauma. - Mechanical heart valves. - ABO incompatibility. - PCH. - Infections. - Snake bites. - RBC surface abnormalities. - **Extravascular Hemolysis:** - Inherited or acquired (not always present in early childhood). ### Hemolytic Anemia Symptoms - Jaundice. - Fatigue. - Tachycardia. - Pallor. - Pigmented gallstones (if chronic). - Leg ulcers. - Splenomegaly. - Dark urine. ## Polycythemia - Diseases characterized by surplus RBC and an increased viscosity of blood. - Causing symptoms. - Hemolytic transfusion reaction: Destruction of RBC after a transfusion mediated by host antibodies. ### Ways to Classify Anemia - **Production Defects:** Anemia, chronic diseases, renal diseases, Fanconi anemia, Blackfan-Diamond syndrome, parvovirus infections, drug toxins. - **Survival Defects:** Hemoglobinopathies, immune hemolytic anemia, hemolysis, membrane and metabolic abnormalities. - **Maturation Defects:** Vitamin B12 deficiency, folate deficiency, iron deficiency, sideroblastic anemia, lead poisoning, hemorrhage, hypothyroidism. ## Anemia of Blood Loss ### Acute Blood Loss - Rapid loss of 10% or more blood volume through hemorrhage. - Can result in shock. - Caused by loss of intravascular volume (can cause cardiovascular collapse, shock and death if massive). - Blood volume is restored by an intravascular shift of water from the interstitial fluid compartment. - Results in hemodilution and decreases hematocrit. - **Symptoms of acute blood loss:** Tachycardia, Intravascular volume. - Treatment: Intravenous fluid resuscitation with normal saline. ### Chronic Blood Loss - Induces anemia when loss regeneration of marrow or when iron is low. - **Iron deficiency anemia is most common when dietary intake or absorption of iron is limited and hemoglobin can’t be made.** ## Hemolytic Anemia - A hereditary defect of RBC or damage by extrinsic factors that increase RBC destruction by phagocytes. - **Symptoms:** - RBC lifespan decreases to 120 days instead of the expected 120 days. - Increased erythropoietin levels. - Increased erythropoiesis. - **Physiological destruction** of RBC takes place in macrophages (in the spleen, liver and bone marrow). - **Accumulation of hemoglobin degradation products** is created as part of the process of red cell hemolysis. - **Extravascular hemolysis:** Premature destruction of RBC in phagocytes. - Caused by alterations that render RBC less deformable. ## Pathogenesis of Hemolytic Anemia - **Hyperbilirubinemia and jaundice** from degradation of hemoglobin by macrophages. - **Splenomegaly** from hyperplasia of phagocytes in the spleen. - **Bilirubin-rich gallstones and pigmented stones:** Bilirubin is a product of broken hemoglobin. It is also involved in cholecystitis secondary to bile duct blockage. ## Intravascular Hemolysis - Cause: - Mechanical injury (microcirculation, bad cardiac valves, physical trauma, RBC burst). - Intracellular parasites (Malaria and Clostridium release enzymes that digest RBC membranes). - **Complement fixation:** - Antibody recognizes and binds RBC antigen. ## Hereditary Spherocytosis (HS) - Inherited disorder (autosomal dominant). - Cause: Inherited defects in the RBC membrane skeleton proteins. - This causes membrane loss which forms spherocytes (that lose deformability). - Biconcave RBCs released from marrow become spheres due to the loss of membrane. - RBC lifespan is 10-20 days compared to normal 120 days. - RBCs are sensitive to osmotic lysis in hypotonic solutions (water in the RBC). - RBCs have increased MCHC from dehydration. **Symptoms:** - Anemia (chronic hemolytic). - Splenomegaly. - Jaundice. - No erythropoiesis. - Can also be asymptomatic. **Spherocytosis Shape:** Smear as small, dark stain (hyperchromic). Lack central pallor and have polychromatic reticulocytes. **Treatment:** Transfusion, splenectomy (to treat anemia, but can also damage the spleen). ## Hereditary Elliptocytosis (HE) - Autosomal dominant disorder. - Cause: Defective tetramerization of cytoskeletal spectrin (causes elliptocytes/ovalocytes). **Hereditary pyropoikilocytosis:** Variant of HE where RBC are sensitive to damage from heat. - Peripheral blood smear shows RBCs of every shape and size. **HE manifests as lifelong hemolytic anemia.** ## Glucose-6-Phosphate Dehydrogenase Deficiency (G6PD) - Causes impaired reduction of glutathione (which protects against oxidative damage by free radicals), hemolysis (infections, drug initiators). - It is caused by an infection or by drug initiators. - Reduced RBC to protect themselves from oxidative injuries -- Hemolysis (when defenses are compromised). - Abnormal hexose monophosphate shunt or glutathione metabolism (from impaired enzyme function). - Reduced glutathione protects hemoglobin and RBC membrane from oxidative damage. - When not enough G6PD enzyme (hemolytic anemia), RBCs break faster than they are made (this occurs because they are more susceptible to oxidative damage). - Genetically X-linked trait (males at higher risk). - Hundreds of variations. - Some variants cause miss-folding of proteins leading to proteolytic degradation. ## Sickle Cell Disease - Autosomal recessive disorder caused by a single point mutation in an amino acid. - 6th codon of B-globin, glutamate replaces valine residue, making sickle hemoglobin (HbS). - Normal hemoglobins: Hemoglobin A (α2β2) and fetal hemoglobin (HbF) (α2γ2). ### Sickle Cell Disease Effects - **Hemoglobin crystallizes** at low O2 tension. - Hemoglobin S causes hemolysis and microvascular occlusion. - **Unstable hemoglobin** causes chronic hemolysis with Heinz bodies. - **Heinz bodies:** RBC inclusions composed of denatured hemoglobin. - **Hemoglobin increases O2 affinity** (polycythemia). - **Hemoglobin doesn't want to be oxidized** (cyanosis). - **Changes shape and function** of hemoglobin, increasing the chance of blockages. ### Sickle Cell Disease During Childhood - **Splenomegaly.** - **Spleen shrinks.** - **Anemia.** - **Jaundice.** **Symptoms** - **Vascular occlusion** and resultant ischemia causing severe pain in long bones, abdomen, and chest. - **Pain crisis** caused by localized obstruction of microvasculature by sickled cells. - Major pathological manifestations: - Chronic hemolysis. - Microvascular occlusions. - Tissue damage. - **Increased MCHC** from higher HbS and intracellular dehydration. **Morphology** - **Peripheral blood:** - Has sickled cells. - Reticulocytes. - Target cells. - **Howell-Jolly Bodies:** Small nuclear remnants from asplenia. - **Bone marrow:** Hyperplastic (often compensatory, erythroid hyperplasia). ## Thalassemia - Hemoglobinopathy caused by mutations in genes. - Can cause abnormal globin chains causing disease. - Has reduced production of normal globin chains. **Hemoglobin structure** - 4 polypeptide chains - **Major adult hemoglobin A (HgA) is made of 2 alpha and 2 beta chains.** - The 2 alpha chains are made by a pair of alpha globin genes on chromosome 16. - The 2 beta chains are made by a single beta globin gene on chromosome 11. **Cause**: - Genetic abnormality in either alpha or beta globin chain synthesis. - Imbalance in hemoglobin synthesis causes reduced hemoglobin and hemolysis. **Symptoms**: Microcytic and hypochromic blood picture. Damages developing and mature RBC. Anemia. Hypoxia. **Syndromes**: - 3/4 or 4/4 genes deleted (syndrome). - If only 2 or 1 are affected, it is a trait. ### Beta Thalassemia (Mediterranean / Cooley’s Anemia) - Symptoms: Severe, transfusion dependent anemia from infancy, splenomegaly, marrow expansion, bony deformities and premature death. - Cause: Deficient synthesis of beta chain from inheritance of two genes. - Blood picture: Microcytic, hypochromic anemia (beta chains cannot be replaced by gamma). - Symptoms: Severe anemia, growth retardation, iron overload. - Morphology: RBC abnormalities, anisocytosis, poikilocytosis, microcytosis, hypochromia. Increased reticulocytes. ### Polychromasia - A disorder where abnormally high numbers of immature RBCs are in the blood stream. - Codocytes: “Target cells,” RBCs that look like a bullseye. ### Beta Thalassemia Minor - More common than beta thalassemia major (Still inherited but less severe than major). - Pts heterozygous for the Beta^T or Beta⁰ allele. - Symptoms: - Mild anemia. - Usually asymptomatic. - Mild erythroid hyperplasia in bone marrow. - Blood smear: - RBC abnormal. - Hypochromia. - Microcytosis. - Basophilic stippling. - Target cells. ### Alpha Thalasssemia - Cause: Inherited deletions that result in absent synthesis of alpha globin chains (normally 4 alpha globin chains). - Severity depends on how many genes are affected. **Silent Carrier State:** Deletion of single a-globin gene --> barely detectable reduction in a globin chain synthesis (mostly asymptomatic). ### Thalassemmia Trait - Deletion of 2 alpha globin genes from 1 chromosome (α/α- or α/ -- ) or deletion of 1 alpha globin from 2 chromosomes (α/ --). - Clinically identical behavior, but different implications for children of affected individuals. ### Hemoglobin H Disease - Cause: Deletion of 3 alpha globin genes. - Abnormal alpha globin gene = alpha chain reduced & tetramers of beta globin. - Symptoms: Hypoxemia (decreased O2 affinity), RBC sequestration and phagocytosis in spleen, severe anemia. ### Hydrops Fetalis - Most severe form of alpha thalassemia. - Cause: Deletion of all alpha globin genes. - Extra gamma globin chains in the fetus deliver little O2. - Symptoms: Severe pallor, generalized edema (shown in 3rd trimester of pregnancy). ## Paroxysmal Nocturnal Hemoglobinuria - Cause: Acquired mutations in phosphatidylinositol glycan complementation group A gene (PIGA), an enzyme essential for membrane proteins. - Hemolytic anemia is caused by a genetic defect. - PNH is an RBC membrane defect (DAF) which increases susceptibility to complement mediated lysis. - X-linked, inactive X chromosome involved. ## Immunohemolytic Anemia - Antibody binds to antigens on RBC membrane, causing premature destruction. **Direct Coombs Anti-Globulin Test:** RBC mixed with antibodies whose target is specific for human immunoglobulin or complement. ## Hemolytic Anemia Causes ### Trauma - Mainly in people with cardiac valve prostheses and microangiopathic disorders. - Microangiopathic hemolytic anemia most common with DIC, TTP and HUS. ### Mechanical - Intravascular hemolysis of RBC from abnormal forces. - Traumatic hemolysis from cardiac valves. - Microangiopathic hemolytic anemia occurs when the small vessels become narrowed by thrombi. ## Anemias of Diminished Erythropoiesis ### Megablastic Anemia - Cause: Impairment of DNA synthesis - Ineffective hematopoiesis. - Distinctive morphology changes. - **Symptoms:** - Vitamin B12 deficiency. - Folic acid deficiency. ### Hemolytic Disease of Newborn - Cytotoxic: Responsible for tissue damage in hemolytic disease of newborn. - Cause: - Antigen on PM recognized as foreign, B-cells ready to produce antibodies. - Anti-body-induced hemolytic anemia. - Mother and fetus are not blood compatible. - Fetus inherited RBC antigen determinants that are foreign to mother. ## Type 2 Hypersensitivity Reaction - Antibody on PM is “foreign” -- Bell ready for antibody production, antibody binds to antigen-- Activate complement. ## Folate Deficiency - Cause of megaloblastic anemia. - **Megaloblastic:** Appearance of hematopoietic precursor cells in marrow - Appearance: Nuclei are large & immature. - **Symptoms** - Ineffective erythropoiesis - Hypercellular marrow - Impairment of DNA synthesis ## Pernicious Anemia - A form of megaloblastic anemia. - Cause: Gastritis that impairs production of intrinsic factor (needed for B12 uptake). ### Vitamin B12 (Cobalamin) - Dietary vitamin that needs intrinsic factor to be absorbed. - **Symptoms:** Autosomal attack on gastric mucosa. Can’t make healthy RBC. ## Iron Deficiency Anemia - Iron is needed to make hemoglobin. - Iron is internalized in RBC cytoplasm and incorporated into protoporphyrin to yield heme (no iron = no hemoglobin). - Iron is toxic by itself at high levels. ### Symptoms - RBC hypochromatic and microcytic. - Low hematocrit. ### Transferrin - A glycoprotein that binds iron and transports it to the plasma and cells. ### Hepcidin - A small peptide that regulates iron absorption. ## Signs of Iron Deficiency Anemia - **Low:** RBC count, MCV, MCHC. - **High**: RDW, platelet #. ### Peripheral Blood - Hypochromatic, microcytic RBC. - Scattered elliptocytes. ### Serum Ferritin - Test to confirm iron deficiency (below 10 μg/L). ## Lead Poisoning (Plumbism) - Symptoms: - Abdominal pain - Cognitive impairment - Vomiting - Seizures - AMS. - Presentation: Microcytic, hypochromic anemia. - Effects: RBCs. Renal epithelium. Nervous system. ### Effect of Lead - **Inhibition of heme synthesis** in maturing erythrocytes. - **Decreased survival** of mature erythrocytes. ## Sideroblastic Anemia - Iron incorporated into porphyrin to make heme. - **Ringed Sideroblasts:** Morphological expression of abnormal sequestration of iron in mitochondria (mainly in the bone marrow). - Peripheral blood: - Anemia - Dimorphic RBCs - Normocytic macrocytes - Hypochromic microcytes - **Cause:** Abnormal utilization of iron during erythropoiesis. - 2 forms: Hereditary and acquired ## Symptoms of Sideroblastic Anemia - Physeal fatigue, pale skin, conjunctival pallor, bronze colored skin, malaise, headache, shortness of breath, palpitations. ## Anemia of Chronic Disease - Sustained systemic inflammation. - Iron utilization in marrow. - Suppresses hematopoiesis. - Symptoms: - Mild. - Refractory. - Hyporegenerative. - Normocytic. - Normochromic anemia - Cause: Impaired RBC production and chronic disease that produce systemic inflammation. ## Aplastic Anemia - Symptom of chronic primary hematopoietic failure and *attendant* pancytopenia. - **Cause:** Suppression of multipotent hematopoietic stem cells. - **Symptoms:** Bone marrow hypocellularity and pancytopenia. - Acquired: Idiopathic. ## Pure Red Cell Aplasia - A primary marrow disorder where only erythroid progenitors are suppressed. ## Polycythemia - Abnormal high RBC count (mean increase in hemoglobin). ### Causes - Decreased plasma volume from dehydration causes hemoconcentration. - **Absolute:** Increase in total RBC mass from abnormal hematopoietic precursors.