MLAB 13115- Hematology Keri Brophy-Martinez Fall 2007

1. MLAB 13115- HematologyKeri Brophy-MartinezFall 2007 Unit 13: Hemolytic Anemias: Intracorpuscular Defects/ Hemoglobinopathies

2. THE HEMOGLOBINOPATHIES • Hemoglobinopathy is a condition in which abnormal hemoglobins are synthesized in the bone marrow. • These are qualitative abnormalities in the hemoglobins that are formed normally but have abnormal substitutions of an amino acid in the globin chain. The most common chain affected is the β chain

3. Normal Adult Hemoglobin • Hb A : 95-98% • Hb A2: 2-3% • Hb A1: 3-6% • Hb F: <1%

4. Sickle Cell Anemia • Hemoglobin SS (homozygous) α2β2S • Inheritance of Hgb S gene from both parents. • Valine is substituted for glutamic acid at the sixth position on the β globin chain in the hemoglobin molecule. • When oxygen tension is lowered or pH decreases, gel polymerization occurs and leads to sickling of the red cell. Sickled cells cannot flow freely through the microvasculature of joints and the spleen, furthering the hypoxic environment. This causes intense pain. Tissue necrosis occurs and patients infarct their spleen at an early age (autosplenectomy). RBC’s trapped within spleen. • Note: Symptoms do not appear in infants until after 6 months of age due to the persistence of Hgb F causing a low level of Hgb S.

5. Sickle Cell Anemia • Occurs with greatest frequency in tropical Africa. Incidence in African-Americans is 0.26% • Sickle cell carrier state confers an advantage to Plasmodium falciparum malaria due to preferential sickling of parasitized cells

6. Sickle Cell Anemia: Clinical Features • Hemolytic anemia with jaundice • Organ damage due to ischemia, where the blood flow is blocked due to abnormally shaped RBC’s. • Bone and joint abnormalities (swelling of joints) • Severe pain • Leg ulcers • Stroke and pulmonary complications

7. Sickle Cell Anemia: Lab Tests • CBC and retic • Hgb: 6 - 8 g/dl • RBC: decreased • Retic: 5-20% (unless in aplastic crisis) • Evaluation of the peripheral smear • Sickle cells, target cells, red cell fragments, polychromasia, NRBC’s, Pappenheimer bodies and Howell-Jolly bodies

8. Sickle Cell Anemia: Lab Tests • Hemoglobin electrophoresis on cellulose acetate and citrate agar gels • Hemoglobins migrate at different speeds when an electrical charge is applied to a solution. Staining the support media (gel) allows you to visibly see a pattern of migration. Several hemoglobins migrate together on cellulose acetate media at pH 8.4, so it is often necessary to perform the electrophoresis on citrate agar medium at acid pH of 6.0 to 6.5 to separate them. • Refer to page 807, Figure 40-1 in textbook for hemoglobin electrophoresis migration patterns on cellulose acetate and citrate agar

9. Sickle Cell Anemia: Lab Tests • Measurement of hemoglobins A2 and F • Hgb A2 level may be slightly increased • Hgb F may persist into adulthood

10. Sickle Cell Anemia: Treatment • Prevention of infection • Hydroxyurea (it is believed to induce production of Hgb F). Using chemotherapeutic agents • Avoidance of situations that could cause a crisis. • Blood transfusion • Treatment of pain • Median age at death • Male: 42 • Female: 48

11. Sickle Cell Trait • (heterozygous) α2β1β16Glu-Val • Patients inherit a normal β globin gene from one parent and a sickle-globin gene βs from the other parent. • Incidence is 8-10% in African Americans. Genetic counseling is recommended for people with the trait. • Usually asymptomatic with occasional episodes of hematuria. • Sickling can occur with drastic reduction of oxygen tension such as severe respiratory infection, air travel in unpressurized aircraft, anesthesia or congestive heart failure. • Exercise that causes a buildup of lactic acid can cause sickling due to lowered pH.

12. Hemoglobin C Disease • (homozygous) α2β26Glu-Lys • Inheritance of Hgb C gene from both parents • Lysine is substituted for glutamic at the 6th position on the β globin chain of the hemoglobin molecule. • In decreased oxygen tension, HbC has decreased solubility and forms intracellular crystals. • Greatest frequency is in West Africa. Incidence in US among African Americans is 0.2%.

13. Hemoglobin C Disease: Clinical Features • Mild chronic anemia with enlarged spleen and abdominal discomfort

14. Hemoglobin C Disease: Lab tests • Mild ↓ H&H • Peripheral smear evaluation • Normocytic-normochromic red cells • 50-90% target cells • Folded cells with HbC crystals intra- or extracellular. • Hemoglobin electrophoresis

15. Hemoglobin SC Disease • α2β16Valβ16Glu-Lys • HbS gene is inherited from one parent and HbC gene is inherited from the other parent. Incidence in the US African Americans is 0.12%

16. Hemoglobin SC Disease: Clinical Features • Milder anemia • Increased blood viscosity causes retinal hemorrhage, kidney necrosis and femoral head necrosis.

17. Hemoglobin SC Disease: Lab tests • Peripheral smear will have target cells, folded red cells and occasional glove-shaped intracellular crystals. • Hemoglobin electrophoresis on cellulose acetate at alkaline pH.

18. Hemoglobin E Disease • α2β226Glu-Lys • Substitution of lysine for glutamic acid at the 26th position on the β globin chain of the hemoglobin molecule. Occurs with greatest frequency in the southeast Asia region

19. Hemoglobin E Disease: Clinical Features • Anemia is mild to absent • Target cells might be present

20. Hemoglobin S/β-Thalassemia • To be discussed