1. Thalassemia
Gerald A. Soff, M.D.

2. Case: CC
• C.C./HPI:
– 27 year old woman, immigrant from Taiwan, with mild,
chronic anemia since childhood.
– Asymptomatic, very active, runs 3-5 miles, several
times per week.
• Fam Hx:
– Father and several paternal relative with thalassemia.
• PMHx, PSHx: Negative
• Social History: Recently married, contemplating children.
• Physical exam: Normal

3. Case CC: (2)
Test Results Normal
WBC 5.2 X 103/ul 4-11
Hgb 11.5 g/dl 11.5-16
Platelet 249 X 103/ul 160-400
RBC 5.29 X 106/ul 4.0-5.2
MCV 67 fl 82-98
Ferritin 55 ng/ml 6-200
Iron, Total 93 mcg/dl 34-165
TIBC 355 mcg/dl 235-425
LDH 139 U/L 12-246

4. CC (3) Hemoglobin Electrophoresis
Hgb Results Normal
Hgb A1 97.2% 96.3-98.7%
Hgb A2 2.8% 1.9-3.5%
Hgb F None detected 0-2%

5. CC (4)
• Diagnostic Molecular: (Performed at
Mayo)
• HBA: “Two alpha globin genes are
deleted in the cis, i.e., on the same
chromosome (Southeast Asia type).”
• HBB: “Beta-Globin DNA Mutations:
Negative”

6. CC (5)
Issues/Interventions?

8. Hemoglobin;
Globin Tetramer
• Hemoglobin can consist
of two alpha chains and
2 beta class chains of
globin.
• 2 2; Hgb A
• 2 2; Hgb A2
• 2 2; Hgb F

9. Globin Chain Switching During
Development

10. Hemoglobins in Development

11. Thalassemia
• -Thalassemia; Decreased Production of -globin
chains
• -Thalassemia; Decreased Production of -globin
chains.
• Results in decreased Hemoglobin synthesis and a
microcytic/hypochromic anemia
• Severity of disease is depending upon the number of
mutant genes.

12. Thalassemia Syndromes
• Depending on genetic severity;
• Chronic anemia, high out-put cardiac states
• Hepatosplenomegaly due to extramedullary hematopoiesis.
• Transfusion-Dependent (Thalassemia major)
– Need for iron chelation.
• Due to increased marrow turnover, need for folic acid
replacement.

13. Severe Thalassemia (Major)

14. Pathophysiology of Thalassemia Major

15. Thalassemia Major;
Expansion of Marrow Disrupts Bone Cortex
Prior To Transfusion After Transfusion Skull, From
Therapy Therapy Autopsy

16. Pigment Gall Stones in Thalasemia;
(Common in all chronic Hemolytic Anemias)

17. Iron Overload in Thalassemia
(Don’t give iron for all microcytic
anemias!)

18. Geographic Distribution of
Thalassemia/Hemoglobinopathies

19. Hemoglobinopathies and Thalassemia;
Role in Malaria
• The malarial parasite
(Plasmodium) has an
essential intra-
erythrocyte stage.
• Sickle trait (as well as
G6PD deficiency)
causes red cell lysis
prior to successful
replication of parasite.

20. Alpha Thalassemia
• Most frequently due to absence of one or more of the
normal complement of 4 alpha genes
• The fewer the alpha genes present the more severe the
clinical syndrome
• Absence of 1 or 2 genes produces only hypochromia and
microcytosis – alpha thal trait
• African-Americans – 30 % lack 1 alpha gene. Frequently
mistaken for Fe deficiency.
• No increase in HbA2

21. -THALASSAEMIA
• Particularly common in South East Asia and
the Far East. Also frequent in Africa and the
Mediterranean but is rare in northern Europe.

22. -Thalassemia Syndromes
• Normally four genes for -Globin, two on each of chromosome
16.
– +; One normal/one mutant on chromosome.
– 0; Both mutant genes on one chromosome. (Mostly in
Asians)
• If two genes mutant, Thalassemia minor
– Hemoglobin electrophoresis normal.
• If three genes mutant; Hemoglobin H Disease
– Hgb H; 4 Tetramer
• If all four genes mutant; Hydrops Fetalis;
– Hgb Barts; 4 Tetramer

23. Gene Deletions in Alpha
Thalassemia

24. MOLECULAR CLASSIFICATION OF
-THAL
• Gene mapping allows deletions to be identified.
• Loss of 1 of 2 genes on a single chromosome (- α/)
– α+ thal. haplotype.
• Loss of both genes on a single chromosome (- -/)
– α° thal. haplotype.

25. “Golf ball” appearance of Hb H ( 4) stained
supravitally with brilliant cresyl blue
(Reticulocyte Stain).

26. Alpha Thalassemia
Hb Bart’s-Hydrops Fetalis
• Fetus inherits 2 chromosomes 16, both lacking any alpha
genes.
• No HbF can be made.
• Hb Bart’s – γ4 tetramer - high O2 affinity, hyperbolic
oxyhemoglobin dissociation curve
• Fetus suffers from anoxia, develops intrauterine congestive
heart failure, total body edema.
• Death in utero or shortly after delivery.

27. Hydrops Fetalis

28. -Thalassemia
• Two types of mutant alleles;
• 0; Absence of expression. Typically a mutation
in coding region of gene (On chromosome 11)
• +; reduced expression of globin gene. Typically
promoter mutation.

29. β-Thalassaemia Geographic
Distribution
• Mediterranean area
• Northern Italy
• Greece
• Algeria
• Saudi Arabia
• Southeast Asia

30. -Thalassemia Syndromes
Type Heterozygous Homozygous
0 Thalassemia Minor; Thalassemia Major;
Hgb A2 >3.5%, MCV Absent Hgb A
<75
Hgb A + F = 100%
+; Thalassemia Minor; Thalassemia Major or
Hgb A2 >3.5%, MCV intermediate;
<75 Hgb F; 70 - 80%
Hgb A2; >3.5 - 5% (variable)
Hgb A; 10 - 20%

31. Beta Thalassemia Major:
Cooley’s Anemia
• Beta thalassemia gene present on both chromosomes 11 (βº/βº,
βº/β+, β+/β+)
• Cooley’s Anemia – Homozygous βº/βº thalassemia
• May not be the same mutation on both chromosomes 11
• Complete or very severe absence of beta globin
• Preserved expression and relative increase of HbF and A2, but
insufficient to support life (ie. does not fully replace HbA)
• Life-long severe transfusion-dependent anemia

33. Beta Thalassemia Major
• Hypochromia
• Microcytosis
• Anisocytosis
• Poikilocytosis
• Nucleated RBC’s
• Hepato-splenomegaly
• Growth defects
• Bone defects
• Transfusion dependence

34. - vs. -Thalassemia
• Since only the -chain is synthesized of the -class of
globin chains, the ratio of Hgb. A, A2, and F is not altered
in -Thalassemia.
• In -Thalassemia, Hgb A2 ( 2 2 ) and HgB F ( 2 2) levels
as % of total Hgb are increased due to selective loss of -
globin.
• Hemoglobin electrophoresis can distinguish between -
and -Thalassemia. (best for quantitation by column
chromatography).

36. DNA Analysis For Thalassemia
• Reference Laboratories now have standard
assays available to screen for common
globin gene mutations or sequence full
DNA.

37. Differentiation of Microcytic Anemia
• Iron deficiency vs. Thalassemia
• In iron deficiency, red cell
number, Hemoglobin, and MCV
are all proportionally reduced.
• In Thalassemia, the MCV is
disproportionately low, and red
cell number is “spared.”

38. Prevention Of Cooley’s Anemia
Prenatal Diagnosis And Genetic
Counseling
• Cyprus: Thalassemia first identified in 1944
• 1970 – prediction that in 40 years 78000 units/yr
would be needed to treat all affected children
• 40% of population would need to be donors
• Total cost of transfusions would exceed health budget
• Prevention program yielded 90% reduction in
thalassemia births

39. Reduction In β-Thalassemia Births In
Sardinia After Prenatal Screening

40. DELTA-BETA THALASSAEMIAS
• Deletions of δ and β genes (δβ-
thalassaemia).
• Hb A2 is normal and Hb F is unusually
high in the heterozygote. Hb A and Hb
A2 are absent in the homozygote.

41. Hemoglobinopathies That Mimic
Thalassemia

42. Hemoglobin Constant Spring
• A mutation in the alpha globin gene produces an product that
is abnormally long, (Loss of normal stop codon.
• The messenger RNA for hemoglobin Constant Spring is
unstable, reduced peptide translation.
• The Constant Spring alpha chain protein is itself unstable.
• The result is a thalassemic phenotype.
• Distinct “slow moving hemoglobin” on electrophoresis.

43. Hemoglobin Lepore
• Uneven cross-over of genes for
beta and delta chains.
• Results in decreased production
of Lepore.
• “no phenotypic evidence of
thalassemia in persons with
hemoglobin anti-Lepore,
because no beta chain deficiency
accompanies the latter
condition.”

44. Treatment Of Transfusion-
Dependent Thalassemia
• Transfuse 3-4 units blood every 3-4 weeks
• Maintain hemoglobin at 11-12 g/dL
• Iron chelation – daily s.c. infusions of Desferal
via syringe pump over 6-8 hrs
• Oral chelating agents in development
• Exjade – has recent FDA approval for oral
administration