Red Blood Cell Anomalies and Anemias

Red Blood Cell Anomalies and Anemias

• Study notes on red blood cell anomalies and anemias, including anisocytosis and variations in RBC size.

Red Blood Cell Anomalies

Anisocytosis

• Anisocytosis refers to the variation in the size of red blood cells (RBCs).
• It correlates with Red Cell Distribution Width (RDW), which is an index of variation of cell volume reported in automated analyzers.
• The normal range for RDW is 11.5%-14.5%, while for newborns, it's 14.2%-19.9%.
• A smear may show a mixture of normocytes, microcytes, and macrocytes.
• Normocytes are 6-8 µm in size, microcytes are less than 6µm, macrocytes are greater than 8µm, and megalocytes are 9-12 µm.

Red Cell Size

Normocytic RBCs

• Normocytic RBCs are normal in size and normochromic.
• Central pallor in RBCs is normal.
• MCV and MCHC are within normal range.
• Examples include during blood loss (acute posthemorrhagic anemia), hemolytic anemia, anemia of chronic diseases, and aplastic anemia.

Microcytic RBCs

• Microcytic RBCs are smaller than normal and hypochromic.
• Central pallor in RBCs is more than 1/3
• MCV is reduced (MCV < 80 fL); MCHC is reduced (<30 g/dL).
• Examples include thalassemia, anemia of chronic inflammation, iron deficiency anemia, lead poisoning, and sideroblastic anemia.

Macrocytic RBCs

• Macrocytic RBCs are larger than normal.
• Central pallor in RBCs is normal.
• MCV is increased (MCV > 100 fL); MCHC is normal (31-36 g/dL).
• Examples include megaloblastic anemia and non-megaloblastic anemia.

Four Ways to Detect Anisocytosis

• Anisocytosis can be detected by observing the nucleus of a small lymphocyte in a peripheral blood smear.
• By MCV value
• Also by RDW value, calculated from RBC histogram; an abnormally wide histogram indicates an abnormal RDW.
• RDW is markedly elevated in newborns but decreases to adult levels by 6 months.

RDW values and associated conditions

• Normal RDW (little or no anisocytosis) can indicate anemia of chronic disease or alpha or beta-Thalassemia trait.
• Increased RDW (anisocytosis) indicates iron deficiency anemia or sickle cell-beta-thalassemia.
• Decreased MCV (microcytic) is associated with anemia of chronic disease or alpha or beta-Thalassemia trait.
• Normal MCV (normocytic) is associated with G6PD or reticulocytosis.
• Increased MCV (macrocytic) is associated with liver disease/alcoholism or aplastic anemia.

RBC Histogram

• A visual display of cell size (X-axis) and cell frequency (Y-axis).
• Automated hematology analyzers produce histograms for RBCs, WBCs, and platelets.
• Two parameters calculated from RBC histogram: MCV and RDW.
• Instruments count cells with volume sizes between 36 fL and 360 fL as RBCs
• While the RBC histogram can measure cells as small as 24 fL, cells counted in the 24-36 fL range aren't included in the RBC count.
• Macrocytic RBCs cause the curve to shift right; microcytic RBCs shift it left.
• A bimodal RBC histogram curve indicates two RBC populations, seen in blood transfusions or cold agglutinin disease.

RBC Chromasia

• RBC chromasia refers to the color of red blood cells, indicating their hemoglobin content.

Normochromic RBCs

• Have a normal amount of hemoglobin with normal color.
• Central pallor does not exceed 1/3 of the red cell's diameter.
• MCHC is 32-36%.
• Seen in regular and pathological conditions like acute blood loss, hemolytic or aplastic anemia, sideroblastic or iron deficiency anemia, or thalassemia.

Hypochromic RBCs

• Have central pallor greater than 1/3 of the diameter of the red cells.
• MCHC is less than 31%.
• Anulocyte is a RBC with a thin rim of hemoglobin and a large, clear center, observed in iron deficiency anemia.

Hypochromia Grading

• 1+: Area of central pallor is 1/2 of cell diameter.
• 2+: Area of pallor is 2/3 of cell diameter.
• 3+: Area of pallor is 3/4 of cell diameter.
• 4+: Thin rim of hemoglobin.

Hyperchromic RBCs

• No central pallor; not biconcave but biconvex, thick RBC through microcyte in size.
• MCHC is over 36%.
• "Spherocyte" is the current terminology.
• Tests include autohemolysis and osmotic fragility to detect hyperchromic cells.

Polychromatophilic RBCs

• Have a blue-gray tint, indicating young RBCs with residual RNA.
• Indicates more erythropoietic activity
• Will show up as reticulocytes when stained with brilliant cresyl blue.

Dimorphic Anemia

• Presence of hypochromic and normochromic cells in the same film.
• Can indicate sideroblastic or iron deficiency anemias, or hypochromic anemia after transfusion.

Poikilocytosis

• Variation in the shape of RBCs

Megalocyte

• Abnormal nucleus due to deficiency synthesis of DNA due to lack of B12 or folic acid deficiency

Acanthocyte

• Spheroid with irregular spikes/spicules.
• Due to abnormal ratio of lecithin and sphingomyelin (phospholipid layer).
• Associated with abetalipoproteinemia, cirrhosis, heparin administration, etc.

Echinocyte (Burr Cell, Crenated RBC)

• Regular scalloped short projections evenly distributed.
• Abnormality in the lipid content of the membrane.
• Deficiency in ATP due to prolonged storage of anticoagulated blood or exposure to hypertonic solution.
• Associated with uremia, kidney or liver disease, or pyruvate kinase deficiency.

Codocyte (Target Cell)

• Cells with a central area of Hgb, a colorless ring and a peripheral ring of Hgb.
• Due to deficiency in the phospholipid and cholesterol content in the RBC membrane.
• Associated with thalassemia and liver disease or hemolytic anemia.

Leptocyte

• Has a thinner central portion.
• Represents a thinner variant of target cell.

Elliptocyte

• Elliptical (cigar-shaped) RBC due to a defect in the cytoskeleton with decreased membrane protein band 4.1.
• Related to abnormality in spectrin component of RBC membrane.
• Iron deficiency anemia, thalassemia major, myelophthisic anemia

Ovalocyte

• Oval (egg-shaped) cell with bipolar aggregation of hemoglobin.
• Related to reduction in membrane cholesterol.
• Associated with megaloblastic anemia and myelodysplasia.

Spherocyte

• Small, round, dense RBC with no central pallor due to abnormal spectrin component of the RBC membrane.
• Indicates extravascular hemolysis.
• ABO hemolytic disease of the newborn and hereditary spherocytosis.

Stomatocyte (Mouth Cell)

• Elongated RBCs with slit-like pallor area due to increased permeability to sodium.
• Thalassemia minor and hereditary spherocytosis.

Drepanocyte (Sickle Cell)

• Thin, dense, elongated RBC pointed at each end due to Hgb S polymerization.
• Sickle Cell Anemia and Hemoglobin SC Disease.

Schistocyte (Schizocyte)

• Fragment produced by RBC damage from fibrin, altered vessel walls or prosthetic heart valves.
• DIC and artificial heart valves.
• Indicates intravascular hemolysis.

Keratocyte (Helmet Cell)

• RBC fragment in shape of a helmet.

Blister Cell

• Cell with eccentric vacuole

Knizocyte

• RBC with triangular shape

Folded Cell

• RBC with membrane folded over

Dacryocyte (Teardrop Cell)

• RBC with a pointed extension resembling a teardrop or pear, unable to pass through splenic sinuses.
• Anemia and myelofibrosis

Pyropoikilocyte

• Damaged erythrocyte due to sensitivity to warm temperature

Semilunar Bodies

• Fragments of RBC membrane resembling crescent cells.
• Can indicate a malarial infection.

RBC Inclusions

Siderocyte

• Mature erythrocyte with iron-containing granules

Sideroblast

• Immature erythrocytes with iron-containing granules

Hemosiderin

• Presence of iron stained with Perl's Prussian Blue

Howell Jolly Bodies

• Remnants of DNA in RBCs.

Pappenheimer bodies

• Erythrocytes with clusters of iron granules near the periphery, stainable with Wright's stain.

Cabot rings

• Nuclear remnant with a ring-shaped appearance, remnants of mitotic spindles.

Heinz bodies

• Denatured hemoglobin, stained with supravital stain.
• Observed in bite cells or degmacytes.

Basophilic Stippling or Punctillia

• RBC with blue-purple granules distributed throughout the cytoplasm, remnants of ribosomes or precipitated RNA.
• Coarse stippling may be seen in lead poisoning.

Hemoglobin C Crystal

• Hexagonal crystal of dense hemoglobin within the RBC membrane.

Hemoglobin SC Crystal

• Quartzlike crystal of dense hemoglobin protruding from the RBC membrane

Parasitic Inclusion

• Maurer's dots, Schauffner's dots, James dots, and Zimmerman's dots representing parasitic infections

RBC Inclusions (Supravital Stain Only)

• Hemoglobin H, Heinz bodies, and Reticulocytes, identified using supravital stains like brilliant cresyl blue.

Miscellaneous RBC abnormalities

Autoagglutination

• Clumping of RBCs due to antibodies, enhanced by cold agglutinins.

Rouleaux Formation

• Aligned RBCs linear appearing like stacked coins caused by gamma globulins in the blood

Polychromatophilia or Diffuse Basophilia

• RBCs with blue-gray and pink cytoplasm, corresponding to reticulocytosis.

Staining Characteristics for inclusions

• Staining characteristics for inclusions using Feulgen, supravital, and Wright stains demonstrate the presence of DNA and RNA.

Grading of Erythrocyte Morphology

• Best area to observe: red cells are barely touching each other but not overlapping

Grading of Erythrocyte Morphology (Numerical Scale Descriptions)

• Normal appearance erythrocytes = 0
• Few erythrocytes displaying abnormality = 1+
• Moderate amount of abnormal erythrocytes = 2+
• Several increase in abnormal erythrocytes = 3+
• Severe abnormality = 4+

Anemia Definition

• Decrease below normal of the hemoglobin concentration/RBC count
• Decrease in the total circulating red cell mass to below normal limits
• Decrease in the oxygen-carrying capacity of the blood to hypoxia.
• May be absolute, caused by impaired RBC production or increased RBC destruction.
• May be relative, as is seen in pregnancy, macroglobulinemia, postflight astronauts
• Compensatory mechanism; release of young RBCs ("shift reticulocytes") seen in PBS.

Classes of Anemia

• Morphologic (based on red cell size and hemoglobinization).
• Etiological

Etiology of Anemia

• Impaired Red Blood Cell Production, Disturbed Proliferation and Maturation of Erythroblasts, defective DNA synthesis, etc.
• Increased Red Cell Destruction (Hemolytic Anemias), Intrinsic or Extrinsic

Ineffective Erythropoiesis

• Hypoproliferative and maturation disorders when RPI is below 2.0
• Blood loss/hemolytic anemia when RPI is above 3.0

Algorithm for morphologic classification of anemia

• Microcytic: MCV < 80 fL. iron deficiency and thalassemias
• Marcocytic: MCV > 100 fL. Non megaloblastic and Megaloblastic causes.
• Normocytic: MCV between 80-100 fL: Causes include Anemia of Chronic disease and Hemolytic anemias

Iron Deficiency Anemia

• IDA is a common nutritional disorder.
• Dietary deficiency or inadequate intake of iron in infants
• Impaired absorption of iron in the duodenum.
• Chronic blood loss in the GIT, urinary tract, genital tract, or respiratory tract
• Parasitic infection with hookworm.

Stage 1 Iron Deficiency

• Storage iron depletion, progressive loss of storage iron.
• Adequate iron to maintain normal hemoglobin level only serum ferritin decreases

Stage 2 Iron Deficiency

o Transport iron depletion; Iron-deficient erythropoiesis - There is exhaustion of the storage pool of iron. o Lowering of serum iron and transferrin saturation levels without anemia. o Bone marrow shows iron-deficient erythropoiesis.

Stage 3 Iron Deficiency

o Functional iron depletion; Frank anemia; Iron deficiency anemia - There is impaired hemoglobin production. o Morphologically, there is first reduction in the size (microcytic) and later increase in the central pallor (hypochromia) of RBCs.

Diagnostic Order

• Diagnostic order for Iron deficiency Anemia:
• 1. Absent of iron stores
• 2. Decreased serum ferritin
• 3. Decreased serum iron
• 4. Increased TIBC
• 5. Decreased iron saturation
• 6. Microcytic hypochromic anemia

Clinical signs of Iron deficiency anemia

• Nonspecific symptoms include Fatigue, palpitations, breathlessness, weakness and irritability
• Physical symptoms include angular stomatitis, glossitis, gastritis, and koilonychia
• Patterson-kelly or Plummer-Vinson syndrome

Lab Diagnosis - Iron deficiency anemia

• MCV
• Red blood indices (MCV, MCH, MCHC)
• Platelet count
• Bone marrow assessment (gold standard) negative prussian blue reaction

Stage 1 Laboratory Findings

sTfR >200 µg/dL Ferritin <15 µg/L.

Stage 2 Laboratory Findings

STIR >200 µg/dL TIBC 350-450 µg/dl. Ferritin <15 µg/. Serum iron 10-15 µg/dL

Stage 3 Laboratory Findings

STIR->200 µg/dL TIBC: 350-450 µg/dL Red cell protoporphyrin > 200µg/dL. Ferritin <15 µg/L. Serum iron 10-15.µg/dL

Anemia of Inflammation

• Central feature: Sideropenia because Sideropenia
• Associated with systemic disease tuberculosis

Etiology of Anemia of Inflammation

• When systemic body iron levels DECREASE DECREASE hepcidin production INCREASE Iron release
• Production of tumor necrosis factor-a and interleukin-1 from activated macrophages and interferon-y from activated T impairs the proliferation of erythroid progenitor cells
• Shortened red blood cell lifespan shortens

Sideroblastic Anemias

• Diseases that interfere with the production of protoporphyrin
• Ringed/Ring Sideroblasts

Pharmocology treatments

• Some patients experience at least modest improvement of anemia with pharmacologic doses of pyridoxine
• *Pyridoxine is a cofactor in the first step of porphyrin synthesis in which glycine is condensed with succinyl coenzyme A to form aminolevulinic acid.

Sideroblasts types

• type I- at least 4 ferritin aggregates per cell
• Type II More than 6 ferritin aggregates per cell
• Type III Large iron-laden mitochondria forming a ring around the nucleus

Mutations of Sideroblasts

• Mutations in the genes for proteins involved in mitochondrial processes such as heme synthesis and energy production.
• Acquired - Ethanol inhibits enzymes

Diagnosis and Lead exposure for Sideroblasts

• At Least 155 of normoblasts are Type III
• Normocytic, normochromic anemia

Porphyria information

• Hereditary conditions Impairs the production of protoporphyrin

Hemolytic Anemias

• Breakdown of normal RBCs occurs in the macrophages of the bone marrow, liver, and spleen.
• Increased red cell prouction

Test

Placed in acidified serum and RBC lysis as a positive result