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Hemoglobinopathy

Hemoglobinopathy. John Matthews and Dilys Rapson. Hemoglobin structure. α. β. β. α. heme. Hemoglobins in normal adults. α. β. α. γ. α. δ. β. α. γ. α. δ. α. HbA. HbF. HbA 2. 98%. ~1%. <3.5%. Hemoglobin structure. α. β. β. α. heme. Heme. Globin.

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Hemoglobinopathy

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  1. Hemoglobinopathy John Matthews and Dilys Rapson

  2. Hemoglobin structure α β β α heme

  3. Hemoglobins in normal adults α β α γ α δ β α γ α δ α HbA HbF HbA2 98% ~1% <3.5%

  4. Hemoglobin structure α β β α heme

  5. Heme

  6. Globin

  7. The Oxygen Dissociation Curve pAO2 pVO2 normal e.g. α2β2 abnormal e.g. β4

  8. Hemoglobin synthesis 25% 25% 0.5% 1.5% 48% α α γ δ β α α γ δ β 25% 25% 0.5% 1.5% 48% Chromosome 16 Chromosome 11

  9. Hemoglobinopathydefinition An inherited mutation of the globin genes leading to a qualitative or quantitative abnormality of globin synthesis

  10. Structural hemoglobinopathy Amino acid substitution in the globin chain e.g. sickle hemoglobin (HbS)

  11. The Thalassemias • Syndromes in which the rate of synthesis of a globin chain is reduced • beta thalassemia - reduced beta chain synthesis • alphathalassemia – reduced alpha chain synthesis

  12. Sickle Cell Anemia (HbSS) • β6 glu to val • ‘tactoids’ at low oxygen tension • sickled red cells • small blood vessel occlusion • tissue infarction

  13. Sickle Cell Anemia – blood film SickleCells Erythroblasts Howell-Jolly Body

  14. Sickle Cell Anemia – EM of red cell showing ‘tactoids’

  15. Sickle cell anemia – clinical features • Hemolysis • Occlusion of blood vessels by sickled red cells

  16. Sickle Cell Anemia - treatment • Opiates and hydration for painful crises • Pneumococcal vaccination • Retinal surveillance • Hydroxyurea • Transfusion for serious manifestations • Stem cell transplant • Support, folate, iron chelation

  17. Sickle Cell Trait • Heterozygous state for HbS (HbAS) • No serious clinical consequences • Sudden death during intensive training • Hematuria, isosthenuria (renal papillary necrosis)

  18. Beta thalassemia • Impaired production of beta chain • beta thalassemia minor – heterozygous (or trait) • beta thalassemia major - homozygous

  19. Beta thalassemia trait • No symptoms • Mild microcytic anemia

  20. Beta thalassemia major • No beta chain produced (no HbA) • Severe microcytic anemia occurs gradually in the first year of life • Marrow expansion • Iron overload • Growth failure and death

  21. Beta thalassemia major Male 18 years

  22. Beta thalassemia major treatment • Transfusion • Iron chelation • Stem cell transplant

  23. Alpha thalassemia

  24. Hemoglobinopathy-antenatal diagnosis • Test partners of heterozygous or affected individuals • Antenatal diagnosis from DNA obtained by chorionic villus sampling, or by amniocentesis

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