1. Hemoglobinopathies- Part II
Nemer El Mouallem MD
VCU Health system
05/30/2018

2. Hemoglobinopathies - part 2
Structural mutants resulting in a thalassemic like phenotype:
Hb Lepore
Constant Spring
Hb E
Decreased solubility
Crystallization
Hb C disease
Unstable hemoglobins
Congenital Heinz body hemolytic anemia
Hb Koln
M hemoglobins (familial cyanosis/congenital methemoglobinemia)
Abnormal oxygen affinity mutations
High affinity hemoglobin (familial erythrocytosis, Hb Chesapeake)
Low affinity hemoglobin (familial cyanosis, Hb Kansas)

3. Reminder- Human Globin Genes

4. Hemoglobin Lepore Condition affecting globin chain synthesis
Fusion of β and δ chains
Decreased synthesis of beta like globins
Homozygotes
Beta thal major phenotype (more commonly intermedia)
Hb electrophoresis: 8-30% Hb Lepore, 70-92% HbF
Heterozygotes: beta thal minor phenotype

5. Hemglobin constant spring
Non- deletional form of alpha thalassemia
Mutation in stop codon of α2 globin decreased synthesis of normal α globin and increased synthesis of abnormal chain with extra 31 amino acids
Homozygous constant spring:
HbH phenotype: intermittent transfusions needed
Near normal MCV

6. Hemoglobin E Beta-thalassemia like hemoglobinopathy
β codon 26: Glu  Lys leading to alternative splicing  decreased mRNA production of normal β globin- similar to β+
Second most common hemoglobin variant: 30 million worldwide, mostly in SE Asia
RBC cytoplasm: precipitated alpha chains, increased oxidant stress

7. Hemoglobin E trait
Heterozygotes (hemoglobin E trait, HbAE) not usually anemic, but may have minimal degrees of microcytosis and hypochromia. Hemoglobin analysis shows approximately 30 percent HbE, 1 percent HbF, and 70 percent HbA.
●Homozygotes (hemoglobin E disease, HbEE) minimal anemia along with hypochromia, target cells, and prominent microcytosis. Hemoglobin analysis shows >90 percent HbE and no Hb A, with the remainder being HbF.

8. Hemoglobin E

9. Hemoglobin E HbE/β0 thalassemia
Phenotype similar to severe thalassemia intermedia
HbE 60-85%, HbF 15-40%
Mild to moderate microcytic hemolytic anemia
Ineffective erythropoiesis and iron loading

10. Hereditary persistence of fetal hemoglobin
Causes
Deletions involving β and δ genes
Inactivation of HbF suppressor by decreased expression of KLF1 transcription factor
Up-regulation of γ chain synthesis
Almost 100% HbF in homozygotes
Clinically silent

11. Hemoglobin C Beta globin chain mutation
Less soluble than HbA  forms hexagonal crystal
Presence induces red cell dehydration  High MCHC
HbC trait: HbAC; benign carrier trait
HbC disease: HbCC; mild hemolysis and splenomegly, minimal to moderate anemia
Prevalent in Atlantic West Africa
HbSC variant

12. Unstable Hemoglobin diseases
Congenital Heinz body anemia
Rare autosomal dominant mutation
Leads to defective binding of heme to globin
About 200 variants  heterogenous phenotype
Heinz bodies, oxidative membrane damage, hemoylsis

13. Unstable hemoglobin diseases
Normocellular to microcytic hemolytic anemias
Heinz bodies detected by new methylene blue or bromocresol green
RBC stability testing : heat stability test or isopropanol stability test
Molecular testing for mutation analysis

14. Unstable Hemoglobin Diseases

15. Unstable Hemoglobin Diseases
Avoid oxidants
Transfusions as needed
Splenectomy in severe cases

16. Hemoglobin M disorders
Typically autosomal dominant: can be a mutation in the α, β, or γ globin chains
Single amino acid substitution in the heme pocket globin chain
Hereditary methemoglobinemia and cyanosis
Amino acid substitutions in heme pocket leading to Fe oxidation: Fe2+ to Fe3+

17. Hemoglobin M disorders
Clinical Manifestations:
Asymptomatic cyanosis
Slate grey/brownish skin
No dyspnea
Normal life expectancy

18. Hemoglobin M disorders
Diagnosis
Abnormal SpO2
Hb electrophoresis, Hb spectrophotometric absorbance
Methemoglobin <30%
Definitive diagnosis is made by DNA sequencing
Cyanosis not reversible with methylene blue or Vit C
Treatment: Major issue is misdiagnosis and unnecessary treatments
Cytochrome B5 or CB5 reductase deficiency variants

19. Acquired forms of Methemoglobinemia

20. Abnormal oxygen affinity mutations
Hemoglobin O2 Dissociation Curve

21. Abnormal oxygen affinity mutations

22. Hemoglobins with high O2 affinity
Low p50 (left shift), inadequate tissue oxygenation
Autosomal Dominant
Familial erythrocytosis
Alpha or beta chain can be affected
Example: Hb Chesapeake

23. Hemoglobins with high O2 affinity
Diagnosis:
Hb electrophoresis, HPLC
PCR or gene sequencing
Treatment: Polycythemia mild, phlebotomy not needed

24. Hemoglobins with low O2 affinity
Much less common
High p50 (right shift in dissociation curve)
Asymptomatic cyanosis, though oxygenation to
tissues is adequate
No treatment required
Example: Hb Kansas

26. Screening Prenatal screening In the US, per ACOG:
-CBC with RBC indices to all pregnant women
-Hemoglobin electrophoresis or HPLC for low MCV or MCH OR
based on ancestry: African, Mediterranean, Middle Eastern, Southeast Asian, or West Indian descent

27. Screening

28. Examples
Which hemoglobinopathy is this? HbA 20% HbA2 5% HbF 75%

29. Examples
Which hemoglobinopathy is this? HbA 71% HbE 28% HbF 1%

30. Example
Which hemoglobinopathy is this? HbA 90% HbA2 7% HbF 3%

31. Examples
Which hemoglobinopathy is this? HbA 0% HbE 70% HbF 30%

32. Example Which hemoglobinopathy is this? HbA 0% HbA2 4% Hb F 96%