2. OUTLINE
• Thalassemia terminology and biology
• β-Thalassemia Major
• β-Thalassemia Intermedia and trait
• α-thalassemias and other subtypes
• Principles of iron chelation treatments
3. THALASSEMIA OVERVIEW
• Heterogeneous group of quantitative globin chain defects
• Inherited anemia
• Microcytic anemia, ineffective erythropoiesis, iron overload,
hemolysis
• 1-2% of the world population
• Malaria-endemic regions
4. Regions Where Thalassemia Is Endemic
Higher prevalence in
Mediterranean and
Asian subcontinent1
Tropical Sub-tropical
Malarial Belt
75% of immigrants to
the United States are
from areas
where thalassemias
are prevalent2
1. Weatherall. BMJ. 1997;314:1675. Reprinted with permission.;
2. Cohen et al. Hematology (Am Soc Hematol Educ Program). 2004:14.
5. THALASSEMIA TERMINOLOGY
• Thalassemia-”from the sea” (Mediterranean)
• β-thalassemia: β-globin defect
• Africa, Asia, Near East, India
• Often point mutations
• α-thalassemia: α-globin defect
• Often deletions
• (0)=zero, absent chain
• (+)=plus, present but in reduced amounts
• Major, Intermedia, minor are clinical terms based on transfusion
• Other hemoglobinopathies alter syndrome
6. Prenatal and Neonatal Human Globin Synthesis
Normal Developmental Hemoglobin Switching
Olivieri N. NEJM, 1999; 341:99-109
Clinical Detection of β Thalassemia in the Newborn
7. THE FETAL HEMOGLOBIN SWITCH AS A
TARGET
Compounds that increase
HbF
Hydroxyurea
Decitabine
Butyrate
Fatty acids
8. ALPHA AND BETA CHROMOSOMAL
EXPRESSION DURING DEVELOPMENT
β-like genes
Hemoglobins
Developmental
period
α-like genes Chromosome 16
Chromosome 11
Hb Gower 1
(ζ2ε2)
Hb Gower 2
(α2ε2)
Hb Portland
(ζ2γ2)
Embryonic
Hb F
(α2γ2)
Fetal
HbA2
(α2δ2)
HbA
(α2β2)
Adult
0 10 20 30 40 50 60
ζ2 α2 α1 θ1
Gγ Aγ δ βε
Hofmann et al. Biochem J. 1995;306:367.
Nathan and Oski. Hematology of Infancy and Childhood. 4th ed. 1993:786.
9. COMPLEX GENETICS: PHENOTYPE VS
GENOTYPE
• >200 disease causing β-globin
gene mutations
• full deletions uncommon
• Co-inheritance of a-thalassemia
and increased gamma-chain
synthesis may offset genetic
imbalance of a/B chains
• Other chromosome genetics
responsible
• 128 molecular α-globin mutations
• Full deletions usually responsible
• A-hemoglobin stabilizing factors
Vichinsky Pediatrics 2005
10. HEMOGLOBIN TYPES BY CHAIN
• α2β2: Hb A Predominant adult hemoglobin
• α2δ2: Hb A2 minor hemoglobin
• α2γ2: Hb F Fetal hemoglobin
• Normal tetramers of hemoglobin have important properties
• High solubility
• Reversible oxygen binding
• Free chains assemble in thalassemia
• A4: hemoglobin
• γ4: Hb Bart’s
• β4: Hb H
11. QUESTION 1: HEMOGLOBIN SYNTHESIS
• Which of the following is the initial site of hemoglobin synthesis?
• Fetal Yolk sac
• Liver
• Spleen
• Bone marrow
• Thymus
12. QUESTION 2: AT WHAT AGE CAN A CHILD BE
DIAGNOSED WITH B-THALASSEMIA?
• A-Immediately at birth
• B-2 months of age
• C-6 months of age
• D-12 months of age
13. Rachmilewitz & Giardina
Blood 2011
Unpaired α-chains are
less soluble=more toxic
compared to β chains
β thalassemia has more
ineffective erythropoiesis
vs α
15. BETA THALASSEMIA MAJOR
• β0/β0
• Inherit 2 β-thalassemia alleles from chromosome 11
• Anemia, ineffective erythropoiesis
• Regular transfusions required for survival
• 200 known beta mutations
• Ethnic group predicts mutation
• Promoter, abnormal cleavage and polyadenylation
• Impaired mRNA splicing, impaired translation
16. WHEN TO INITIATE TRANSFUSIONS
• Unable to maintain hemoglobin >7g/dl
• Facies, poor growth, extramedullary hematopoiesis,
fractures
• Require transfusion within the first year of life
• Progressive anemia
• Hypersplenism, fatigue, weakness, surgery, pregnancy,
leg ulcers
• Pulmonary hypertension, cardiac disease, thrombosis
www.thalassemia.org
20. PEDIATRIC AND ADULT POPULATIONS ARE
FROM DIFFERENT ETHNIC BACKGROUNDS
<20 Other
(Asian)
>20
Italian/Greek
Vichinsky Pediatrics 2005
21. Β-THALASSEMIA MAJOR PATIENTS LIVE
INTO ADULTHOOD
• Transfusion 1-2 units of RBCs every 2-4 weeks
• Splenectomy
• Iron chelation
• Management of other co-morbidities
22. CURRENT TRANSFUSION GOALS
• To minimize transfusional iron loading
- Splenectomize < 200 mL/kg/yr RBCs
• To maintain pre-transfusion Hgb > 9-10 gm/dl
- 15 mL/kg monthly approx. 0.3 – 0.6 mg/kg/day Fe
- Short transfusion intervals q 2 wks
• Partial suppression of erythropoiesis
• Inhibition of GI iron absorption
23. MINIMIZE TRANSFUSION REQUIREMENTS
WITH SPLENECTOMY: GOAL = < 200
ML/KG/YR
400
360
320
280
240
200
160
120
80
40
0
Before
splenectomy
After
splenectomy
Years after splenectomy
400
350
300
250
200
150
100
50
0
1 2 3 4 5 6 7 8 9 10 17
Transfusedblood(mL/kg/y)
Transfusionrequirement(mL/kg/y)
Cohen et al. Am J Hematol. 1989;30:254.
24. QUESTION 3: WHICH OF THE FOLLOWING IS
TRUE REGARDING ADULTS WITH B-
THALASSEMIA MAJOR?
• A-Adult patients may have a decreasing need for transfusion as they age
• B-Because of gonadal dysfunction from iron overload, adult females cannot
carry children, no successful pregnancies have been reported in thalassemia
major
• C-Serum hepcidin levels are significantly elevated in thalassemia
• D-The most common cause of death in adults with thalassemia major is
arrhythmias from cardiac siderosis
25. HEPCIDIN: THE MASTER REGULATOR
OF IRON HOMEOSTASIS
• 25-aa peptide hormone
• Predominantly produced
and secreted from liver
• Inhibit iron uptake in
intestine and prevent iron
release from macrophages
• Induce internalization and
degradation of ferroportin
(FPN), the sole iron exporter
Ganz & Nemeth, BBA, 1823:1434, 2012
26. ERYTHROFERRONE AND HEPCIDIN
• Hepcidin
• 28 AA peptide
• Degrades Ferroportin
• Reduces iron absorption
• Abnormally low in thalassemia major and
intermedia
• Erythroferrone
• Iron response hormone
• Responds to Epo signaling
• Reduces hepcidin
Kautz et al Nat Gen 2014
27. THALASSEMIA INTERMEDIA IS A MILDER
PHENOTYPE
• β+/β+ or β+/β0
• Iron overload occurs even in the absence of transfusion
• Thrombophilic state: splenectomy, reactive platelets, EC damage, complement activation
• 10-34% thrombosis prevalence
• Short term transfusion during stress/infection/pregnancy
• Alternatives to transfusion
• Splenectomy
• Hydroxyurea
• Recombinant human Erythropoeitin
• Most patients require transfusions in their 3rd-4th decade of life
28. WHEN TO TRANSFUSE
THALASSEMIA INTERMEDIA (NTDT)
• Based on the patient and not hemoglobin alone
• Acute exacerbations of anemia1
• Hypersplenism, consistently declining hemoglobin
level2
• Fatigue1, weakness, poor quality of life2
• Infection, surgery, pregnancy, leg ulcers2
• Pulmonary hypertension, thrombosis, cardiac disease
1. Olivieri. N Engl J Med. 1999;341:99.
2. Camaschella and Cappellini. Haematologica. 1995;80:58.
30. TRANSFUSION THERAPY IMPROVES
COMPLICATIONS OF THALASSEMIA
INTERMEDIA
Transfusions in β-Thalassemia
Complication RR on Transfusion
Extramedullary hematopoiesis 0.06*
Pulmonary hypertension 0.33*
Heart failure 0.06*
Thrombosis 0.28*
Cholelithiasis 0.36*
Abnormal liver function 1.56
Leg ulcers 0.39*
Hypothyroidism 13.3*
Osteoporosis 3.10*
Adapted from Taher OPTIMAL CARE study Blood 2010
* p<0.05
31. Current Therapy of Thalassemia
Comprehensive Care
Transfusion Visits Bi-Monthly
Compliance Monthly
Comprehensive Medical Visits Quarterly
Psychosocial Assessments Quarterly
Cardiac: EKG, Echo, Holter Annually
Endocrine: Annually
T4, TSH, PTH, GTT, BMD, GH
Hearing and Eye Exams Annually
Skeletal Bone Age / Knee Films Annually
in the growing child
32. ALLOGENEIC
TRANSPLANT IN Β-
THALASSEMIA
• Curative strategy in childhood
• Risk scores based on pre-transplant liver
disease and iron
• Myeloablative/No GVT effect
• HLA-identical sibling donor
• >3000 patients worldwide
• Adults >17 yrs worse outcomes
• 37% non-rejection mortality
Lucarelli Blood Rev 2008
33. B-THALASSEMIA MINOR
• β+/β or β0/β
• Microcytosis with mild anemia
• 1-2 g/dl below normal
• Elevated RBC count
• Decreased Osmotic fragility
• Hyperbilirubinemia
• Cholecystitis
• Pre-natal counseling
www.thalassemia.org
34. Prenatal Diagnosis
• Chorionic villus sampling (CVS):
10 to 12 weeks gestation
• Amniocentesis:
10 to 18 weeks gestation
• Maternal Fetal DNA Analysis:
10 weeks gestation
35. QUESTION 5: WHICH OF THE FOLLOWING IS
TRUE REGARDING ALPHA THALASSEMIA
• Is indistinguishable clinically from beta thalassemia major
• Is always lethal in utero with hydrops fetalis if all four alpha chains are absent
• Is characterized by α+ and α0 mutations that are unrelated to different ethnic groups
• Is a larger genetic risk in Asian patients compared to those of African ancestry as there has
never been a reported case of hydrops fetalis in African patients in this setting
36. ALPHA THALASSEMIAS
• Milder disease
• Not always transfusion dependent
• Pathology related to HbH
• Hydrops fetalis
• Genetic counseling important for carriers
• Question: What is the supravital stain used to identify β-tetramer
inclusions in α-thalassemia?
www.hematology.org
37. --/-- Α-THALASSEMIA (Α0 THALASSEMIA,
THALASSEMIA MAJOR)
• Absent α-chains
• Fetal life sustained by Hb Portland
• Bart’s hemoglobin binds O2, does not release
• Fetal anemia detected by cranial Doppler ultrasound
• Aggressive intra-uterine and post-natal transfusions
• Cannulate intrahepatic fetal umbilical vein for transfusions
• 25-50% with long term developmental/neurologic disorders/Limb defects
• Most cases bridged to transplant
38. HBH DISEASE
• α-/--
• More common in southeast Asians
• Less Ineffective erythropoiesis, more hemolysis in peripheral blood
• Transfusion therapy in some cases
• Deletional vs non-deletional
• Hb Constant Spring is a severe non-deletional form, alpha 2 stop codon mutation
• Non-Deletional is worse
• Pathology related to HbH
• Osteoporosis, poor growth, developmental impairment
• Splenomegaly
39. INCREASED NUMBER OF A-THALASSEMIA
PATIENTS BORN IN THE US
Vichinsky Pediatrics 2005
40. HEMOGLOBIN H DISEASE PHENOTYPES
Vichinsky Cold Spring Harb Perspect Clin Med 2013
41. HEMOGLOBIN H WITH CONSTANT SPRING IS
A WORSE PHENOTYPE THAN DELETIONAL
HEMOGLOBIN H
Vichinsky Cold Spring Harb Perspect Clin Med 2013
42. Α-THALASSEMIA MINOR AND SILENT
CARRIER
• Silent carrier αα/α-
• α-thal minor cis αα/--
• Asian background more common
• α-thal minor trans α-/α-
• African background more common
• No reported African hydrops fetalis from
thalassemia
www.thalassemia.org
43. OTHER THALASSEMIA SYNDROMES
• α-thalassemia and mental
retardation (ATR)
• Large deletions of Chr 16: ATR-16
• Trans deletion on X-chromosome: ATR-
X
• α-thalassemia Myelodysplastic
syndrome (ATMDS)
• Acquired clonal ATRX mutation
• Male >60 with MDS
• Suspect with MDS and microcytosis,
new HbH
• Β-thalassemia and…
• HbS: resembles sickle cell disease
• HbE: similar to beta-thalassemia
• Hereditary persistence of fetal hemoglobin
• Hb Lepore: fusion of δβ globin chains
• NH recombination during meiosis
• Resembles β-thalassemia major
• α-thalassemia vs β-thalassemia in the
same patient
44. IRON OVERLOAD IS THE MAJOR CAUSE OF
MORBIDITY AND MORTALITY IN TRANSFUSION-
DEPENDENT THALASSEMIA
MEASURING BODY IRON BURDEN
Serum Ferritin monthly/quarterly
Liver Biopsy LIC annually
MRI LIC T2* annually
MRI Cardiac T2* annually
MRI Pancreas in early development
45. Adapted from Olivieri and Brittenham. Blood. 1997;89:739.
LIVER IRON AND RISK FROM IRON
OVERLOAD
46. WHEN TO START CHELATION THERAPY
• Red Blood cell transfusions: 10 – 25 RBC units
• Age: 2 – 3 yrs of age
• Liver Iron: > 3 mg / gm dw in TM
> 5 mg / gm dw in TI (NTDT)
• Ferritin level: > 1000 ng / ml in TM
> 500 ng / ml in TI (NTDT)
47. QUESTION: IRON CHELATION THERAPY IS
BEST CHARACTERIZED BY WHICH OF THE
FOLLOWING?
• A-There are currently 4 FDA-approved chelation drugs for first line setting in
thalassemia
• B-Iron chelation in BTM is performed by unloading iron with intensive chelation
therapy followed by cessation, monitoring, and re-treatment if needed
• C-Iron chelation should be escalated in the setting of acute infections to prevent
complications
• D-These medications are toxic when co-administered, and combination therapy is
no more effective than monotherapy
49. DEFERASIROX (ICL670 / EXJADE)
Nick et al. Curr Med Chem. 2003;10:1065.
• Lipophilic but 99% protein-bound
• Long plasma half-life > 12 hrs
• Fe excreted 90% in feces
• Given as once-daily drink
(dispersible tablet in water,
orange or apple juice)
• Oral pill formulation approved
2015 (Jade-Nu)
50. FUTURE GOALS IN
THALASSEMIA
• Improved BMT in adults without sibling HLA-matches
• Hemoglobin F switching
• Gene therapy
• Better chelation
• Improved care of chronic co-morbidities
• Questions?
