§        Quantitative defect → Imbalance of globin chains →

§        Reduced Hb synthesis and anaemia

§        Precipitation of abnormal Hb → haemolysis and ineffective erythropoiesis

§        Alpha

§        Beta

§        Delta-beta

§        Gamma-delta-beta


Thalassaemia major

§        Transfusion dependant

Thalassaemia intermedia

§        Anaemia and splenomegaly

Thalassaemia trait

§        Symptomless


Beta thalassaemia

§        Mediterranean, Middle East and South Asia (Africa as well but less common)

§        Chromosome 11; one gene per chromosome

§        >200 gene defects – categorised into B0 and B+ depending on whether any beta chain is synthesised (B+ is therefore a very broad category)

§        Large variety in phenotype – relates to primary, secondary and tertiary factors:

§        Primary (different gene mutations cause a variety of reduction in alpha chain synthesis)

§        Transcription (deletions / promoter defects)

§        Processing of mRNA (splice junction, consensus sequence, internal IVS, cryptic spice sites in exons)

§        Translation (nonsense, frame shift, initiation site)

§        Post translational instability (exon 3 mutations, other unstable beta chains)

§        Secondary

§        Coinheritance of alpha thal reduces excess alpha chain production improving symptoms

§        Genetic modifiers of gamma chain production

§        Tertiary

§        Factors that affect the complication of disease (eg. iron metabolism / bone disease)



§   Excess of alpha chains

§   Some will bind with delta = A2

§   Some will bind with gamma = F (heterogeneously distributed cf. HPFH)

§   Some precipitate in red cell precursors = intracellular inclusions = ineffective erythropoiesis

§   Some with inclusions enter circulation = haemolysed

§        Increased erythropoieitin – bone marrow expansion and bony abnormalities


Bthal trait

§        Heterozygosity for b thalassaemia

§        Usually asymptomatic – may need transfusion at times of haematopoietic stress e.g. pregnancy or intercurrent illness.

§        FBC

§        Normal or slightly reduced Hb

§        MCV / MCH low

§        MCHC normal

§        RDW normal

§        Blood film

§        Normal ranging to markedly abnormal with:

§        Microcytosis

§        Anisocytosis, poikilocytosis

§        Hypochromia

§        Basophilic stippling

§        Target cells

§        Irregularly contracted cells

§        Elliptocytes move commonly found in iron deficiency

§        HPLC

§        Raised A2

§        NB 4% of A2 is A’2 which is found in the HbS band

§        4-5% usually indicates heterozygosity for B0 or severe B+ thal (usually 3.6-4.2% if heterozygous for B+ thal)

§        Some cases are silent with normal red cell indices and normal A2

§        Some cases are almost silent – with abnormal indices and a slightly raise A2 (referred to as ‘normal A2 Bthal’)

§        Both can be detected using genetic studies and studies of b chain synthesis

§        Rarely patients have normal red cell indices and a raised A2


Dominant Bthalassaemia

Rarely mutations cause symptoms in heterozygotes (mainly splenomegaly / gall stones)

May need blood transfusions

Iron overload can occur


Bthal intermedia

§        Very variable phenotype – results from many different mutations

§        Anaemic but not transfusion dependant

§        Splenomegaly – may develop hypersplenism

§        Leg ulcers

§        Bony deformity

§        Transfusions may be needed at times of stress and can become necessary in later life

§        Gall stones

§        Iron overload

§        Gonadal failure

§        Extramedullary tissue can form tumour like masses in the mediastinum or pleura.  Occasionally affect the spinal cord

§        Congestive cardiac failure may occur


§        Blood film

§        Similar to Bthal trait but more severe:

§        Hypochromia

§        Microcytosis, anisocytosis, poikilocytosis

§        Basophilic stippling

§        Polychromasia

§        Possibly circulating erythroblasts

§   Raised HbA2 (more than Bthal trait)

§   Raised HbF


Bthal Major

§   Severe disease - presents in first year of life (as HbF falls) and transfusion is required to sustain life beyond early childhood (by definition)

§   Usually due to Bthalhomozygote or compound heterozygotes (very rarely heterozygotes have the same clinical phenotype)

§   Can result from compound heterozygosity with a thalassaemic haemoglobinopathy – e.g. HbEBthal0 (less commonly Hb Malay)

Clinical features

§   Pallor

§   Failure to thrive

§   Splenomegaly - later hypersplenism (worsens anaemia / can cause thrombocytopenia)

§   Hepatomegaly

§   Bone pain and tenderness - bone fractures

§   Skull bossing

§   Jaundice, gallstones

§   Stunting of growth

§   Without iron chelation, develop progressive tissue siderosis (hepatic, endocrine, cardiac)

§   Delayed sexual development

§   Commonest cause of death – cardiac failure in third decade

§   Death by 4 years in homozygous B0 / late childhood for homozygous B+ thal


Lab features

§        Hb 2-8

§        Blood film

§        Hypochromia / hypochromic microcytes

§        Marked anisocytosis

§        Poikilocytosis including fragments, teardrops

§        Target cells

§        Basophilic stippling

§        Pappenheimer bodies

§        NRBCs with dyserythropoietic features

§        Increased white count  (but may have neutropenia and thrombocytopenia if massive splenomegaly)

§        Hyposplenic features if previous splenectomy (Howell-Jolly bodies, target cells, lymphocytosis, thrombocytosis, giant platelets)

§        Post splenectomy may contain alpha chain precipitates (can be seen pre splenectomy but less frequent)

§        Leptocytes seen post splenectomy – very flat cells with striking hypochromia

§        Transfused cells

§        Bone marrow

§        Severe dyserythropoiesis with nuclear lobulatoin and fragmentation, basophilic stippling

§        Phagocytic macrophages

§        Pseudo-Gaucher cells

§        Increased iron stores

§        HPLC

§        B0B0 = No HbA, Raised HbF, HbA2 variable

§        B+B0 HbA may be present up to 35%

§        Markers of haemolysis – LDH, bilirubin, haptoglobins




Bthal + other B globin chain abnormality

Sickle cell B-thal

§        Phenotype depends on severity of the B-thal

§        HbS-Bthal+

§        African populations which have mild Bthal – normal survival with only occasional crises

§        HbS and HbA (5-30%) with elevated HbA2

§        HbS-Bthalo

§        Mediterranean population – phenotype often indistinguishable from HbSS

§        HbS with elevated HbA2 and HbF


HbC B-thal

§        Mild haemolytic anaemia

§        Target cells and thalassaemic red cells

§        Diagnosis – HbC predominantly on electrophoresis (also A / A2 depending on severity of Bthal)


HbE B-thal

§        Commonest severe form of thal in SE Asia and Indian subcontinent

§        HbE is inefficiently produced, hence if inherited with Bo = marked reduction in beta globin chain synthesis

§        Can cause severe thalasaemia phenotype (anaemia / bone changes)

§        Very high mortality in early life

§        Diagnosis = HbE and HbF on electrophoresis (may be small amount of HbA if Bthal+)


Delta-beta thalassaemia

§        Deletions of both delta and beta genes (dB-thalo) or creation of a delta beta fusion gene (dB-thal+)

§        Fusion gene produces a delta beta fusion chain which can bind with alpha chains to produce Hb lepore

§        dB-thalo

§        homozygotes - mild anaemia (Hb 8-10) with 100% HbF (can’t make A or A2)

§        thal intermedia

§        heterozygotes – thalassaemia blood picture, with elevated HbF but normal A2

§        HbF is heterogenous distribution cf HPFH which is homogenous

§        Hb lepore (Fusion gene of delta and beta)

§        Homozygotes –

§        Clinical picture Bthal major or thal intermedia

§        HbF and Hb lepore only

§        Heterozygotes (Hb Lepore trait)

§        Blood film and blood count indistinguishable from BThal trait

§        10-15% Hb lepore

§        HbA2 reduced


Gamma-delta-beta thal

§        Actually entire beta cluster is deleted – only found in heterozygotes as homozygosity would be incompatible with fetal life

§        Micreocytosis, basophilic stippling (resembles bthal trait without any F or A2)


Delta thalassaemia

§   Only affects synthesis of A2 and is of no clinical significance

§   However, can cause a falsely normal A2 with Bthal trait – so it will be missed



Hereditary persistence of foetal haemoglobin (HPFH)

§        Persistent fetal haemoglobin in adult life – variety of different definitions (>2% or >8% of cells)

§        Can modify severity of beta-haemoglobinopathies

§        May be mildly polycythaemic due to higher oxygen affinity of HbF


HPFH – sickle

§   70% sickle 30% HbF – mild sickle syndrome


HPFH  Bthal

§   70% HbF – variable phenotype – mild or resembling Bthal intermedia




§        Either the alpha 2 (aTa) or alpha 1 (aaT) gene can be involved (order they appear on the chromosome 16)

§        a2 gene makes about 70% of the alpha chains and deletions have a worse phenotype than a1

§        Deletions and mutations fall into several categories

§        Deletions

§        Part of the gene or the whole of one of the genes = a+

§        Deletion of both genes (a0)

§        Deletion of part of an a2 and an a1 gene with formation of a fusion a gene (a+ phenotype – the two most common mutations a3.7 and a4.2 occur by this mechanism)

§        Deletion of a major upstream regulatory element – a0

§        RNA splice variants

§        Polyadenylation (eg aTSaudiacommon in the Mediterranean gives severe a+ phenotype sometimes regarded as a0

§        Mutations involving RNA translation

§        Initiation / frame shift result in inactivation of the gene

§        Termination sequence mutations result in an elongated alpha chain that is synthesised at a slower rate (e.g. Hb Constance Spring – found in SE Asia = nondeletional alpha+ thal)

§        Mutations causing marked post translational instability of a highly abnormal alpha chain

§        Transactivating abrnormality resulting from mutation in the ATRX gene on the X chromosome which encodes a DNA helicase (results in a syndrome with alpha thal and severe mental retardation)


§        a0

§   Mediterranean (__MED) [1.5% of population]

§   Middle East (__MED) [rare]

§   S Asia (__ SEA, __FIL, __THAI) [3-4% of population]

§        a+

§   Mediterranean (-a3.7 and aTSaudia[10%]

§   Middle East (-a3.7 and aTSaudia)  [variable – up to 80% in Oman]

§   South East Asia (-a3.7-a4.2 and aCSa[around 10%]

§   India / Sri Lanka (-a3.7 and -a4.2) [around 10%]

§   Africa (-a3.7) [around 25% are heterozygous for this mutation / 1-2% homozygous]

§   Melanesia / Polynesia (-a3.7[10%]


§        Cis = --/α α = S Asian  = α o

§        Trans = α-/ α- = African = α+


Heterozygous a+

§   May have completely normal FBC or trivial anaemia and microcytosis (Hb 1g less on average than normal)


Alpha-thal trait (aa/-- or a-/a-)

§   Mild hypochromic microcytic anaemia

§   Confirmatory diagnosis requires DNA analysis

§   Similar to beta thalassaemia trait (hypochromic microcytes, target cells) but HbA2 is normal


Homozygous a+


Heterozygous a0 thal

§   Very mild anaemia with Hb concentration overlapping the normal range

§   RBC increased, MCV and MCH reduced

§   Reticulocyte count 2-3%

§   5-10% HbBarts at birth (higher but overlapping with a+ homozygotes)

§   Will have occasional cells with HbH but this is not a good diagnostic test

§   Definitive diagnosis requires DNA analysis – this is normally done after excluding iron deficiency (with serum ferritin – TF receptor often increased in alpha thal) and beta and delta-beta thalassaemia trait



HbH disease

§   Clinical syndrome arising from a number of different defects (a-/--, --/aTaaTa/ aTa, --/ aCSa....)

§   Homozygotes for severe a+ thal may have the clinical features of haemoglobin H

§   Only occurs where ao-thal is common

§        Greatly reduced alpha chain production leading to the formation of HbH, which has very high oxygen affinity

§        HbH precipitates in bone marrow cells leading to intramedullary death and older red cells leading to haemolysis

§        Haemolysis is more important than ineffective erythropoiesis as the cause of anaemia

Clinical features

§        Variable anaemia (7-10) and splenomegaly

§        Jaundice may be present

§        Survive into adult hood

§        Some patients may have marrow expansion and bony deformity similar to beta thal major

§        Severe haemolytic episodes caused by infection, oxidant drugs, hypersplenism, folate deficiency

Laboratory features

§        Hb 7-10 MCV 50-65 MCH 15-20 MCHC 25-30

§        Film

§        Anisocytosis, poikilocytosis, hypochromia, microcytosis

§        Basophilic stippling may be present

§        Target cells

§        Fragments and tear drops

§        Nucleated red cells may or may not be present

§        HbH 5-40% (normally around 10%)

§        HbA2 normally reduced (1-2%); HbF increased (1-3%)

§        Cresyl blue staining shows golf ball inclusions in 35-90% of cells and Heinz bodies in patients with previous splenectomy

§        Neonates have Hb Barts 10-40%, with HbH at a low percentage



Hb barts (Homozygous inheritance of ao-thal (--/--))

§   Only occurs where ao-thal is common = Se Asia and Mediterranean

§   Very high oxygen affinity resulting in tissue hypoxia

§   Hydrops fetalis

§   Usually still born between 28-40 weeks

§   High incidence of obstetric complications due to the large placenta



Haemoglobin Constance Spring 

§   More anaemia than would be expected with a+ thal heterozygote but tends to be less microcytic

§   Basophilic stippling often prominent

§   Homozygotes – anaemic (10g) with low MCH but only a mild reduction in MCV

§   Reiculocytosis due to shortened red cell survival (only 2-11% HbCS seen)



Alpha thalassaemia associated with mental retardation

§   Chromosome 16 or X chromosome

§   Alpha-thalassaemia associated with MDS

§   X chromosome


Ante-natal screening programs


Should be predicted in fetus

Should be detected in parent

B thal major (Bthalo or HbE/ Bthalo)

Bthal or HbE hetero/ homo or compound

Bthal intermedia



Alpha thalo hetero or HbH

SCA or compound heterozygous states

Hb S/ C/ D-punjab/ O-arab



§        FBC and HPLC

§        Variant Hb – confirmatory testing

§        Test partner

§        Raised HbF – quantitate

§        Kleihauer

§        Homogenous = HPFH

§        Heterogenous – dB-thal – test partner

§        MCH <27

§        Quantitate A2

§        Normal

§        IDA – check ferritin

§        alpha-thal trait

§        normal A2 Bthal trait

¨        ethnic origin

Ø        N. European, African, Afrocaribbean = no action

Ø        Chinese, SE Asian, Greek, Turkish, Cypriot and MCH <25 = risk of ao trait

§        MCH partner – if <25 and same ethnic group

·        DNA analysis

Ø        Mediterranean, Saudi Arabian, S Asian

§        Normal A2 Bthal trait

§        Co-existing B and delta thal trait

·        Test partner

·        Normal = no action

·        Abnormal = DNA analysis

§        Borderline

§        Beta and alpha thal trait

§        Bthal trait and iron deficiency

§        Mild B thal trait

¨        Test partner

Ø        Abnormal = DNA analysis

§        Raised

§        Bthal trait – test partner



§        BMT

§        90% survival if good match and no iron loading

§        Symptomatic

§        Transfusion to suppress erythropoiesis

§        Iron chelation

§        Splenectomy if hyperspleinsm


Diagnosis of haemoglobinopathies

§        FBC

§        Film

§        Sickle solubility (only S)

§        Blood + phosphate buffer (lysing agent and reducing agent) + centrifuge

§        Sickle Hb sickles and is trapped within rbcs

§        Normal Hb is lysed

§        Affected by HbF and transfused blood

§        HPLC

§        Identifies variant Hb by change in electrical charge

§        Quantitates

§        Beware: HIV mimics Bthal trait with an elevated A2, but the meds usually cause macrocytosis

§        HbH and barts elute very quickly and may be missed

§        Confirmatory tests

§        Alkaline electrophoresis (pH 8.2-8.6)

§        A, F, S/G/D, A2/C/E/O-arab

§        Quantitate using elution or spectrophotometry

§        Previously used as screening test

§        Acid gel (pH 6.0-6.2)

§        Do to tell S apart and C apart

§        S and D/G, C and E, C-harlem and O-arab

§        A/D/G/E/A2 run together

§        Iso-electric focusing

§        Suitable for neonates

§        More expensive, but separates more variants than electrophoresis

§        Mass spectrometry

§        Identifies many variants including those silent by other methods

§        Requires small sample volumes

§        Quick

§        Frozen samples can be used

§        Reagents not expensive

§        DNA analysis

§        Definite diagnosis

§        Knowing the mutation with thalassaemia enables some prediction over the severity of the phenotype

§        Required for alpha-thalassaemia


Alpha-chain variants

§        Eg. G-philadelphia

§        Not normally clinically significant as there are 4 alpha genes

§        On HPLC – normally get a peak for A and A2, therefore with a variant – 4peaks – A, Av, A2, A2v


Unstable haemoglobins

§        Easily confused with alpha-chain variants

§        If not detected by HPLC or electrophoresis

§        Extremely unstable or electrophoretically silent

§        Stability tests (hetor isopropanolol)

§        Molecular analysis/ mass spectrometry


High affinity haemoglobins

§        Many are electrophoretically silent

§        Assess affinity using P50

§        Molecular or mass spectrometry




Stem cell transplant in haemoglobinopathies


Beta thalassaemia major

§   Survival at 35 years estimated to be about 90%

§   Indication for transplant

§   <16 years with transfusion dependence

§   HLA identical family donor

§   Consider if >16 years or previously failed transplant


Sickle cell disease

§   Median survival 45 years

§   25% will have stroke by 30 years

§   Indication for transplant

§   Stroke

§   Recurrent chest syndrome

§   Recurrent vaso-occlusive crisis if HU fails (>4 admissions/ year)

§   Transfusion program

§   Emerging – CNS disease



§   Hypertransfuse for 6 weeks to suppress erythropoiesis

§   Busulphan/ cyclophosphamide (reduced dose Bu to reduce long-term toxicity)

§   Campath

§   Stem cells – bone marrow rather than PBSCs due to less GvHD

§   Cyclosporin and methtrexare for GvHD prophylaxis


Improved outcome if limit to those not iron overloaded – can intensely chelate them first

Can venesect once engrafted, see reversal of liver iron and fibrosis

30% mixed chimerism, but all remained transfusion independent



§   Lack of donor

§   Length of treatment

§   Transplant related mortality

§   Log term effects

§   Infertility

§   Pubertal failure (50% = the same for Bthal major)

§   Chronic GvHD 5%

§   Organ toxicity – rare

§   Secondary malignancy <1%


Hb F


Fetal 90% Adults 0.5%

Hb A


Adults 97%

Hb A2


Adults 2.5%

Hb S



Hb SC 



Hb H


2-40% in  a0a+/- Thal

Hb Barts


Fetal Hb found in a0a0 - binds O2 very tightly leading to tissue hypoxia

Hb Gower 1


Earliest fetal Hb

Hb Gower 2


Second fetal Hb

Hb Portland























b thal trait






b thal intermedia






b thal major






HPFH heterozygote






HPFH homozygote






a thal trait





Barts 0-10 at birth

a+ thal (HbH disease)





H 5-40

Barts 20-30 at birth

a0a0 thal





Barts 80-90% at birth

HbE trait





E 30-35

HbE disease





E 95

HbE / b thal





E 60-70

HbE  a thal





E 80

Sickle trait












HbS / b thal






HbS / bthal






HbS / D






HbS / C






Hb Lepore disease





Lepore 8-30

HbD similar to Hb E


Microcytosis with normal A2 and F

§   Alpha thal trait

§   Delta / beta thal coinheritance

§   gdb thalassamia

§   PV complicated by iron deficiency