Anemia: Low RBC and Hemolytic

Question 1

What are the clinical features and laboratory findings in chronic inflammation or infection (malignancy)?What is the treatment?

Answer 1

Dependent upon underlying disease associated: may include fever, arthralgias, arthritis and fatigue. For infection, symptoms and signs relate to the focus (e.g., pain, cough, swelling).Mild-moderate anemia (Hgb 8 -12 gm/dl). Severity proportional to underlying disease; may be normochromic/normocytic or microcytic with some hypochromia. ↓ serum Fe,↓TIBC, nl to ↑ ferritin,↓EPO for Hct,↓retic count.Treat underlying disease (infection, malignancy) to decrease cytokines and interleukins. Treat co-morbid conditions (e.g., iron deficiency). EPO has been shown to be effective in some cases

Question 2

What are the clinical features and laboratory findings in lead intoxication? What is the treatment?

Answer 2

Personality changes, irritability, headache, weakness, wt loss, abdominal pain and vomiting presenting with insidious nature.Mild to moderate anemia.↓retic count. Microcytosis and mild hypochromia. Basophilic stippling.↑zinc protoporphyrin. May see concurrent iron deficiency confounding the diagnosis. Lead levels↑.Chelation therapy

Question 3

What are the clinical features and laboratory findings in renal insufficiency?What is the treatment?

Answer 3

Signs and symptoms may be interrelated with those of renal dysfunction: fatigue, pallor, decreased exercise tolerance, dyspnea, tachypnea. Anemia may have other contributing factors.Usually don’t see anemia until kidney function <40% of normal. Moderate to severe anemia. Hgb 5-9 mg/dl. Normochromic, normocytic.↓retic, occasionally abnormal morphology. EPO deficiency,↓production.Administration of EPO. Treat co-morbid conditions.

Question 4

What are the clinical features and laboratory findings in endocrine related anemia? What is the treatment?

Answer 4

Hyper or hypoactivity, weight gain or loss, systemic skin, nail, hair changes in hyper or hypothyroidism help suggest etiology. Nausea, vomiting, dehydration, weakness and circulatory collapse suggest adrenal insufficiency.Hypothyroidism: mild anemia; most normochromic, normocytic. May be microcytic or macrocytic.Hyperthyroidism: usually normocytic, may be microcytic.Adrenal: mild anemia, normocytic, all have↓reticulocyte count and index.Hormone replacement.

Question 5

Identify other causes for underproduction anemia, including sideroblastic anemia, protein malnutrition, hypothyroidism, hypopituitarism, and decreased affinity hemoglobins.

Answer 5

Sideroblastic anemias are a heterogeneous group of disorders with deposits of iron in mitochondria of erythroid precursors.Two additional causes of underproduction anemia are hemoglobinopathies and malnutrition. Hemoglobin mutations with low oxygen affinity are associated with a right-shifted oxyhemoglobin dissociation curve, decreased oxygen affinity, normal tissue oxygen, and mild anemia because of improved oxygen delivery (in some) and/or hemolysis (depending on the specific mutation).Protein/calorie malnutrition is associated with a normochromic, normocytic anemia. There may be associated vitamin and mineral deficiencies which may also play a role in the anemia.

Question 6

Describe the rationale and indications for the use of erythropoietin and transfusion in the management of underproduction anemia.

Answer 6

EPO is used in specific conditions where there is an absolute deficiency or where EPO levels are decreased out of proportion to the degree of anemia and administration is known to induce a response.With renal insufficiency, the lack of EPO causes anemia

Question 7

Explain the biochemical basis for B12 deficiency and folate deficiency leading to a macrocytic anemia.

Answer 7

Folic acid and vitamin B12 (cobalamin) are critical co-factors for normal hematopoiesis.Deficiencies of folic acid and vitamin B12 profoundly affect the maturation process of red cell precursors in the marrow. The cells increase in size, arrest in S phase of mitosis, and then undergo destruction, resulting in ineffective erythropoiesis and anemia.

Question 8

Identify the dietary sources of vitamin B12 and describe its associated sites and mechanisms of absorption, means of transport, and duration and location of storage.

Answer 8

Vitamin B12 is originally synthesized by bacteria and algae, eventually working its way up the food chain to humans through consumption of meat, eggs, and milk. It is required as a vitamin by animals but not by higher plants - hence, plants do not contribute Vitamin B12 to the diet, and a strict vegan diet can lead to deficiency.Once ingested, Vitamin B12 in food is released in the acid environment in the stomach. The protein carrier, intrinsic factor (IF), is secreted by gastric parietal cells and binds vitamin B12. In the terminal ileum, the B12 is absorbed and released from IF, bound to transcobalamin binding protein II (TcII) and transported to the liver for storage or to other tissues like the bone marrow for use.

Question 9

Identify the dietary sources of folate and describe its associated sites and mechanisms of absorption, means of transport, and duration and location of storage.

Answer 9

Folate is widespread in food. With a typical diet, about one third of the daily folate intake is provided by cereals and bread, another one third by fruits and vegetables, and the remaining one third by meats and fish. Human milk provides enough folate for infants. Overcooking can also lead to loss of folates in food. Dietary folate is absorbed in the jejunum. It is hydrolyzed, reduced and methylated before distribution to the tissues or liver for storage (as methyltetrahydrofolate). The liver stores undergo turnover, secretion in the bile and reabsorption (enterohepatic circulation) supporting a constant supply to tissues.

Question 10

Describe the findings in the peripheral blood and bone marrow in a patient with B12 or folate deficiency.

Answer 10

In the bone marrow, erythroid hyperplasia leading to an alteration of the myeloid:erythroid (M:E) ratio from a myeloid to an erythroid predominance is observed.In peripheral blood, the anemia is variable. There is macrocytosis (MCV >97 fl in adults). The reticulocyte count is decreased, with a reticulocyte index <1.0. On the peripheral smear, macro-ovalocytes and hyper-segmented (%4-5 lobes) neutrophils can be observed. As the anemia progresses, poikilocytes and fragmentation may be seen. In severe cases, neutropenia and thrombocytopenia can be documented, as well as increases in bilirubin and LDH levels due to intramedullary (within the bone marrow) destruction of red cells.

Question 11

Describe vitamin B12 deficiency with respect to: their most common causes, time to development of the clinical state, presence of neurologic and neuropsychiatric abnormalities, and laboratory studies used to make a diagnosis.

Answer 11

The most common cause of Vitamin B12 deficiency is pernicious anemia, due to autoimmune destruction of IF-producing gastric parietal cells.This condition is most common in the older age population.Other causes include failure to produce IF (gastritis, gastrectomy, congenital), malabsorption (multiple disorders), defective transport or storage (TcII deficiency) and metabolic defects in pathways which utilize B12 as a substrate.Vitamin B12 deficiency takes several months to develop because of its long half-life within the body and large hepatic stores. Vitamin B12 deficiency develops more slowly and is more likely associated with malabsorption.Neurologic involvement is classic in B12 deficiency.Direct measurement of serum cobalamin levels. Measurement of plasma homocysteine levels has been used as a more sensitive marker of deficiency of B12 and folate in the tissues.

Question 12

Describe folate deficiency with respect to: their most common causes, time to development of the clinical state, presence of neurologic and neuropsychiatric abnormalities, and laboratory studies used to make a diagnosis.

Answer 12

The most common cause of folate deficiency leading to megaloblastic anemia is inadequate dietary intake. Other causes include malabsorption due to such things as tropical sprue or parasitic infection, inborn errors of folate metabolism (very rare), and increased demands (hemolysis, pregnancy/lactation, rapid growth, psoriasis, myeloproliferative disorders), and Alcohol consumption.The onset of folate deficiency can occur quite rapidly (within weeks), particularly in the setting of malabsorption or alcoholism.Neurological symptoms are not common in folate deficiency.Direct measurement red cell folate levels is useful in diagnosing deficiencies, although there can be problems with these tests. Measurement of plasma homocysteine levels has been used as a more sensitive marker of deficiency of B12 and folate in the tissues.

Question 13

Describe the clinical, laboratory, and autoimmune findings associated with pernicious anemia.

Answer 13

Clinical: Bleeding gums, diahhrea, fatigue, neurological symptoms, pallor, personality and memory changes, SOBLaboratory: Measurement of serum autoantibodies against intrinsic factor, the cobalamin-intrinsic factor complex, and parietal cells is now commonly used to diagnose pernicious anemia, with positivity in more than 60% of adults with the disease.Autoimmune: autoantibodies against intrinsic factor

Question 14

Describe the appropriate therapies for B12 deficiency and folate deficiency.

Answer 14

Cobalamin deficiency: Intramuscular or subcutaneous injections of B12, with a typical schedule being daily for 2 weeks, then weekly until the hematocrit is normal, then monthly for life. If absorption is not an issue, replacement can be oral. In some cases of pernicious anemia, large oral doses given daily can overcome the absorption defect, but correction of the deficiency needs to be documented.Folate deficiency: 1 mg/day orally or parenterally.

Question 15

Provide a definition for hemolysis and describe the two main mechanisms of increased destruction of RBCs, intravascular hemolysis and extravascular hemolysis.

Answer 15

Hemolysis is defined as a decrease in red cell survival or increase in turnover beyond standard norms.Red cells undergoing intravascular hemolysis release hemoglobin into the circulation.With extravascular hemolysis, the red cell is ingested by macrophages of the RE system. The heme is separated from globin, iron removed and stored in ferritin, and the porphyrin ring converted to bilirubin which is released from the cell.

Question 16

Describe the biochemical pathways of breakdown of hemoglobin and the relevant clinical lab tests for hemolysis, including indirect bilirubin concentration, serum LDH level, reticulocyte count, and serum haptoglobin concentration.

Answer 16

With intravascular hemolysis, The tetramer form of hemoglobin is unstable and dissociates into AB dimers which may be immediately bound to haptoglobin. This complex is removed from the circulation by the liver.With extravascular hemolysis, The heme is separated from globin, iron removed and stored in ferritin, and the porphyrin ring converted to bilirubin which is released from the cell. Taken up by a specific transport system in the liver, the bilirubin (lipid soluble) is converted to a water soluble compound by addition (conjugation) of a glucuronic acid.In most, but not all cases, a shortened lifespan of the red cells will result in an increased reticulocyte count and index. Bilirubin is increased if hemolysis is brisk enough to overcome the bilirubin processing system of the liver; A decrease in serum haptoglobin levels, detection of hemoglobin in the urine or plasma, and increase in metheme or methemalbumin all suggest intravascular hemolysis. Release of housekeeping cellular enzymes (SGOT, LDH) from damaged red cells resulting in elevated serum levels may also provide evidence for increased red cell destruction.

Question 17

List the major hereditary and acquired causes of hemolytic anemia.

Answer 17

Congenital and acquired disorders of red cells can be organized by considering extracellular processes which damage red cells (e.g., toxins, antibodies, red cell fragmentation syndromes) and intracellular disorders which result in a shortened lifespan. In the latter category, think outside-in: defects in the plasma membrane/cytoskeleton followed by enzyme disorders and then hemoglobinopathies.

Question 18

Describe the major constituents of the RBC membrane and cytoskeleton; identify the major defects in hereditary spherocytosis. Relate these to the clinical and laboratory findings of the disorder.

Answer 18

Main membrane components include lipids and proteins.The basic pathophysiology is that spectrin, ankyrin or band 3 defects weaken the cytoskeleton and destabilize the lipid bilayer. Loss of membrane and formation of the spherocyte leads to decreased deformability and entrapment in the spleen. Conditioning in the red pulp leads to further loss of red cell membrane and, ultimately, removal by the macrophage.Clinically, patients present with a variable degree of anemia as well as jaundice and splenomegaly. One third have hyperbilirubinemia as neonates. Most inherit the condition as autosomal dominant, although inheritance is sometimes autosomal recessive. Treatment includes supportive care for chronic anemia and intermittent complications and splenectomy, which usually resolves the clinical manifestations.

Question 19

Recognize other erythrocyte membrane disorders (elliptocytosis, pyropoikilocytosis).

Answer 19

Hereditary pyropoikilocytosis is a severe form of congenital hemolytic anemia. It is clinically similar to, and now considered a subtype of, homozygous hereditary elliptocytosis. Hereditary pyropoikilocytosis is an autosomal recessive disorder that produces a molecular defect in spectrin and a partial spectrin deficiency. It manifests as a severe hemolytic anemia with thermal instability of the red blood cells.

Question 20

Interpret an osmotic fragility test for diagnosis of hereditary spherocytosis.

Answer 20

The osmotic fragility test is a formal laboratory test used in the diagnosis of HS. The test measures the in vitro lysis of RBCs suspended in solutions of decreasing osmolarity.Normal RBCs swell in hypotonic solutions and burst when a critical cellular volume is reached. Spherocytes lyse in solutions of higher osmolarity than normal RBCs. Spherocytes are also more sensitive to a decrease in osmolarity.When graphed, compared to normal RBCs, if spherocytes are present, then the curve will be shifted to the left.

Question 21

Explain when splenectomy is indicated for treatment of hereditary spherocytosis.

Answer 21

The pathophysiology of many hemolytic disorders, including hereditary spherocytosis, involves destruction by the spleen, so management of chronic severe anemia sometimes includes splenectomy as a specific strategy. After splenectomy, spherocytes are present on the peripheral blood smear, but RBC survival is relatively normal.

Question 22

Describe the major energy and antioxidant pathways in the RBC.

Answer 22

Embden-Meyerhof pathway: energy is generated through the breakdown of glucose in RBCs due to the absence of mitochondria. Metabolism of glucose to lactate and pyruvate provides ATP necessary to maintain the plasma membrane and cytoskeleton, and energize metabolic pumps to control intracellular sodium, potassium and calcium. ATP generation is critical for RBC survival. Rapoport-Leubering pathway: produces 2,3-diphosphoglycerate which stabilizes the deoxy form of hemoglobin and maximizes transport of O2to tissues. Hexose monophosphate shunt (phosphogluconate or pentose pathway): produces pyridine nucleotide which reduces glutathione and provides protection from oxidant stress. Methemoglobin reductase pathway: maintains the iron in hemoglobin in the ferrous state required for reversible oxygen binding by hemoglobin.

Question 23

How does G6PD deficiency affect energy + antioxidant pathways in RBC?

Answer 23

Inheritance: sex-linked recessive (female carriers, male affected).G6PD is an enzyme in the hexose monophosphate shunt (phosphocluconate or pentose pathway) which protects against oxidant stress. Loss of enzyme activity in the red cell results in inability to restore reduced glutathione.Clinically, G6PD deficiency presents as intermittent episodes of acute hemolytic anemia and hyperbilirubinemia associated with oxidant stress (infection, drugs, ingestion of specific foods—fava beans). May be characterized as a chronic hemolytic anemia punctuated by episodes of acute exacerbation anemia. Cause of neonate hyperbilirubinemia No specific morphologic features are associated with G6PD deficiency. Although occasionally, the smear will show microspherocytosis and “blister” or “bite” cells.

Question 24

How does pyruvate kinase deficiency affect energy + antioxidant pathways in RBC?

Answer 24

Inheritance: autosomal recessive PK is an enzyme which catalyzes the conversion of phosphoenolpyruvate to pyruvate in the Embden-Meyerhof pathway responsible for ATP production within the RBC.PK deficiency results in ↓ ATP production, ↑ 2,3-DPG (right shift in the O2 binding curve), loss of membrane plasticity, ↑ rigidity and ↑ destruction in the spleenPatients present with variable chronic anemia, hemolysis, splenomegaly, gallstones, and aplastic crisis. Lab features: mild to severe anemia, ↑reticulocytes and no specific morphology.

Question 25

Describe the pathophysiology and site of red blood cell destruction of immune-mediated hemlysis due to IgG, IgM, and complement.

Answer 25

Antibodies to universal red cell antigens can cause hemolysis by either intravascular or extravascular destruction. Production of these antibodies can be in response to infection, can be associated with a malignancy or autoimmune disease, or can be drug-induced.Cold antibodies (referring to a 4°C temperature for maximal in vitro effect), typically of the IgM class, transiently bind red cell membrane in cooler areas of the body (fingers, toes, ears, skin). As they move back to central circulation, they avidly activate complement through the C5-9 attack complex which creates holes in the membrane. When they move more centrally, the antibody dissociates itself because of low affinity at higher temperatures, and complement is left to destroy the cell (intravascular hemolysis).Warm (maximal effect at 37°C) antibodies, usually IgG, bind the red cell with high affinity and have no or poor complement activating capacity, inciting the splenic macrophage to antibody-mediated phagocytosis through its Fc receptor.Occasionally, the small amount of C3 also induces phagocytosis through complement receptors. Clearance by phagocytosis results in extravascular hemolysis.

Question 26

Describe the direct antiglobulin test (direct Coombs test) and the indirect antiglobulin test (indirect Coombs test).

Answer 26

Antiglobulin or Coombs tests are used to detect IgG and/or complement on the surface of the cell. The direct antiglobulin test (DAT), also known as the direct Coombs test, evaluates the presence of either IgG or C3d or C4d on the surface of the red cell by the addition of Coombs reagent which has antibodies for IgG, C3d and C4d, causing agglutination.The indirect antiglobulin test (aka -indirect Coombs test) detects the ability of patient’s serum to bind IgG and/or complement to test (normal) red blood cells. By definition, autoimmune hemolytic anemia should have a positive DAT.

Question 27

Distinguish warm antibody-induced autoimmune hemolytic anemia from cold antibody-induced autoimmune hemolytic anemia on the basis of: immunoglobulin class of the antibody, direct antiglobulin test results, and clinical manifestations.

Answer 27

Cold: IgM bind red cell membrane in cooler areas of body, Patients with COLD AIHA have a positive DAT (complement only, no IgG), maximal reactivity at 4˚C and antigen specificity for I or i. As they move back to central circulation, they avidly activate complement through the C5-9 attack complex which creates holes in the membrane. When they move more centrally, the antibody dissociates itself because of low affinity at higher temperatures, and complement is left to destroy the cell (intravascular hemolysis).Warm: (maximal effect at 37°C) antibodies, usually IgG, bind the red cell with high affinity and have no or poor complement activating capacity, inciting the splenic macrophage to antibody-mediated phagocytosis through its Fc receptor. Patients with WARM AIHA exhibit a positive DAT (strong IgG +/- weak complement) with maximal reactivity at 4˚ C and panagglutin without antigen specificity.

Question 28

Outline management options for inherited and acquired hemolytic anemia, including autoimmune hemolytic anemia.

Answer 28

Hereditary Spherocytosis: supportive care for chronic anemia and intermittent complications and splenectomy, which usually resolves clinical manifestations.G6PD deficiency: avoiding oxidant drugs and foods for the most common variants seen in the U.S. For severe cases with chronic anemia, supportive care and folate are included.PK deficiency: supportive care, folate and transfusions if severe anemia continues. Splenectomy may partially ameliorate the disorder.AIHA: identification and treatment of any underlying disorde (lupus, malignancy, etc.).

Question 29

List some of the risks and benefits of splenectomy.Describe when prophylactic antibiotics are indicated post-splenectomy, what antibiotics are used, and the role of vaccination.

Answer 29

Risks: The spleen is critical for clearance of intravascular microbes and in children, is critical to the development of the adaptive humoral response (and is the origin of IgM agglutinins, especially for encapsulated organisms). Most significant complication of splenectomy is overwhelming bacterial sepsis, particularly associated with S. pneumoniae. The risk is greatest in children < 5 years of age. In adults mortality from sepsis is 200 times that of the general population.Benefits: amelioration of symptoms associated with hemolytic anemia.Pre-surgery vaccination protocol: to avoid complication of splenectomy, vaccination against H. influenza b, S. pneumoniae, and Meningococcus takes place before surgery.Prophylactic antibiotics: should be given daily atleast during childhood; and the instruction to see a physician immediately for a febrile illness > 38.5˚ C is imperative.