Hemoglobinopathies

Anwar ZabenArwa MaqboulEias Al-ashhab

Majd BarahmehRa’ed Mashalah

• QualitativeSickle cell anemiaHb C diseaseHb SC disease

• Qauntitative Thalassemias (α and )

 

Hemoglobin Gene

HBB Gene – Hb S Variant

TESTING

Secondary Laboratory Investigation

Cellulose Acetate Hb Electrophoresis - A2/C S F A +

Normal

Secondary Laboratory Investigation

Cellulose Acetate Hb Electrophoresis - A2/C S F A +

NormalHb SS

Secondary Laboratory Investigation

Cellulose Acetate Hb Electrophoresis

- A2/C S F A+

NormalHb SSHb AS

Secondary Laboratory Investigation

Cellulose Acetate Hb Electrophoresis

- A2/C S F A+

NormalHb SSHb ASHb SC

Secondary Laboratory Investigation

Cellulose Acetate Hb Electrophoresis

- A2/C S F A+

NormalHb SSHb ASHb SCHb CC

Secondary Laboratory Investigation

Cellulose Acetate Hb Electrophoresis

- A2/C S F A+

NormalHb SSHb ASHb SCHb CCHB AD

Genetics of Sickle Cell

• Sickle cell is an autosomal recessive disease.

• Therefore, the child can only get Sickle cell if both parents are carriers, not if only one is and the other is normal. They have a 25% chance of getting it if both are carriers

HBB Gene Continued…

SICKLE CELL DISEASE

•This results when both copies of the hemoglobin beta gene have an S mutation.

•All of this person’s beta subunits are replaced by beta S.

Hemoglobin

Alpha Alpha Beta S Beta S

AN INFANT DOESN’T START SHOW SYMPTOMS UNTIL SUFFICIENT HB F HAS BEEN REPLACED BY HB S

•GLUTAMATE IS REPLACED BY VALINE

•PROTRUSION ON Β-GLOBIN

• AT LOW [O2] HB POLYMERIZES

•NORMAL RBCS CAN SQUEEZES ITSELF BUT SICKLED RBCS CANT

symptoms

1-Sickle cell crises : pain episodes

[o2] RBCs assume the sickle-like shape

Those sickle-like shape cant

squeeze like normal RBCs

They clog at the capillaries and block the blood flow

Tissue are not oxygenated resulting in tissue injury or tissue death

Pain episodes crises

Organs that can be affected by sickle crises:

•Brain : could cause a stroke

•spleen and kidney : renal and splenic dysfunction

•Muscle ,bone and joint

•Lungs : acute chest syndrome

2- hemolytic anemia :

Sickled RBCs have shorter lifetime span ( 20 days instead of 120 days ) .

It causes to decrease the number of RBCs anemia

3-hyperbilirubinemia:

RBCs breakdown in spleen

Heme group breakdown produces bilirubin

We can get rid of bilirubin by liver and kidney

Elevated levels of bilirubin causes to color the skin and eyes with yellow color

4- increased susceptibility to infections:

Blood blockage in splenic tissue damages the tissue

making the patient more susceptible to infections

Spleen is responsible for activating immune respond

The proportion of sickle –like shape cells is enhanced by factors that increase the deoxy- Hb S :

PO2

PCO2

[2,3-BPG]

dehydration

treatment

-Analgesics to reduce pain

-Antibiotics ( ex : penicillin) reduces morbidity and mortality due to bacterial infections

-Blood transfusion if the patient has chronic anemia

Blood transfusion complications : -blood borne infections

-hemosiderosis (accumulation of iron in heart ,liver and endocrine organs )

Advantages of sickle cell disease :

1 of 500 newborn African Americans have the homozygous Hb S genes

1 of 12 newborn African American have the trait sickle cell disease

The parasite causing malaria has lifetime span as the normal RBC but sickled RBCs have shorter lifetime span the parasite dies before causing malaria

HemoglobinpathiesOver 800 different mutations of globin chains of human hemoglobin have been discovered

Mutations are classified by the type of mutation.Examples:

• Insertion• Deletion• Base change• Base mismatch (translocation• Duplication• Inversion

These mutations can affect the structure of the protein leading to a deformed protein with malfunction

(e.g.: Mutation in alpha chain, and beta chain)

Hemoglobin C

Hemoglobin C (Hb C) is a beta globin chain mutation, it is caused by the amino acid substitution of lysine instead of glutamine at the Beta-6 position, making the Hb C a less soluble protein than Hb A which is the most abundant hemoglobin protein in adults

(around 90% of total hemoglobin in adults).

Since Hb C is a less soluble hemoglobin than Hb A, this means that Hb C forms hexagonal crystals in the infected blood cell

When Hemoglobin C is present in any of its states (homozygous Hb C, heterozygous Hb SC, and Hb AC) it induces red cell dehydration

Hemoglobin C disease

Some characteristics of homozygous hemoglobin C disease (Hb CC) include:• Cell dehydration• Target cells• Mild hemolysis with no significant anemia (mild

anemia)While heterozygous Hemoglobin C patients are phenotypically normal and the above symptoms doesn’t apply

In homozygous hemoglobin C patients, the Hb C amount in a blood cell is about 100%, while in heterozygous hemoglobin C patients (Hb AC), the percentage of the Hemoglobin C protein is about 35-45% and the rest is normal Hemoglobin (Hb A)

Cell dehydration

Dehydration is caused by abnormal cellular Potassium loss by the K-Cl cotransport pathway (Potassium – Chloride cotransporter) due to interactions between the abnormally positive charged hemoglobin protein and the cell membrane causing an elevated K-Cl cotransport activity

Hemoglobin SC disease

This disease is caused by having double heterozygotes for Beta S and Beta C in patients.

In Hb SC disease, Hb C increases K-Cl cotransport activity, this causes the high intraerythrocytic concentration of Hb S to make polymers, giving the red cell it’s sickled shapeIn Hb SC disease, the cell contains 50% of Hb S and 50% of Hb C, no normal hemoglobin is present (Hb A)

Some Hb SC symptoms

Some of the Hb SC disease symptoms include:• Retinopathy• Ischemic necrosis of bone• Mild painful crisis• Possible asplenia (about 45% of patients older

than 25) leading to sepsis (lowering B.P, dysfunction in kidneys, liver, lungs and CNS)

Methemoglobin

• Normal hemoglobin contains ferrous ions on the center of the heme groups

• Methemoglobin is formed when ferrous oxidized to ferric

• Our blood contains normally about 1% Hb M

Methemoglobinemia

Causes

• Drugs ( nitrates)

• Endogenous products (reactive o intermediates)

• Inherited defects (mutations)

• Deficiency of NADH- Hb M reductase

Effects and Symptoms

• Functional Anemia Chocolate cyanosis Chocolate-cholored blood

• Tissue hypoxia → anxiety, headache , dyspnoea , weakness , lightheadache .

• Rare cases → coma , death.

Treatment

• Methylene blue

Hemoglobin Synthesis

Adult hemoglobin - 96% HbA (α2β2)

Clinically significant variant hemoglobins - usually β abnormalities

α β

α β

Thalassemia Absent or Synthesis of Globin Chains

(Quantitative) Most Frequent in Mediterranean, African,

or Asian Populations - Thalassemia - Chain Synthesis

(Gene Mutations) - Thalassemia - Chain Synthesis (1-3

of 4 Genes Deleted) (SE Asians)

Global Distribution of Thalassemia

Carrier Frequencies for Common Hemoglobin Disorders/WHO- percent

α⁺ thalassemia α◦ thalassemia - Thalassemia

Region

0-40 0-5 0-3 Americas

1-60 0-2 2-18 Easter Mediterranean

0-12 1-2 0-19 Europe

3-40 1-30 0-11 S Asia

10-50 0 0-12 Sub-Saharan Africa

2-60 0 0-13 W Pacific

- Thalassemia's

• α⁺ thalassemia (common /milder form)→ mild hypochromic anemia in homozygous

• α◦ thalassemia's → stillbirth, with toxemic and postpartum complications

• α ⁺ + α◦ thalassemia's → Hb H , varies in severity

Classification & TerminologyAlpha Thalassemia

• Terminology• Silent carrier• Minima• Minor• Intermedia• Major

SymbolismAlpha Thalassemia

• Greek letter used to designate globin chain:

SymbolismAlpha Thalassemia

/ : Indicates division between genes inherited from both parents:

/

• Each chromosome 16 carries 2 genes. Therefore the total complement of genes in an individual is 4

SymbolismAlpha Thalassemia

- : Indicates a gene deletion:

-/

Classification & TerminologyAlpha Thalassemia

• Normal / • Silent carrier - / • Minor -/-

--/• Hb H disease --/-• Barts hydrops fetalis --/--

Silent Carrier of α- Thalassemia

are clinically and hematologically healthy

may have mild reductions in mean corpuscular volume (MCV) and mean corpuscular hemoglobin (MCH).

Normal Hb electrophoresis

Detected by gene analysis

α-thalassemia trait

minimal to no anemia and a low MCV and MCH.

Normal electrophoresis

May show microcytosis and target cells

Identified by gene analysis

Hb H disease / Hb (4) disease

marked variability in degree of anemia

patients may range from asymptomatic to needing periodic transfusions to having severe anemia with hepatomegaly and splenomegaly

Some patients may also suffer hydrops fetalis syndrome in utero

electrophoresis

Hb H disease can be identified by electrophoresis

Hydrops fetalis

( erythroblastosis fetalis): Swollen dead fetus

Usually these infants die in utero or shortly after birth

An excess of Bart hemoglobin (γ4), which is unable to carry oxygen effectively, is indicated

Infants born have massive total body edema with high output congestive heart failure due to the severe anemia

massive hepatomegaly due to heart failure and extramedullary hematopoiesis

- Thalassemia

Silent carrier

- thalassemia trait (+/- anemia)

HbHβ4

disease

Hb Bartγ4

(severe anemia) Hydrops fetalis(lethal in utero)

Chromosome 16

Beta Thalassemia•Inherited disorder (handed to children from parents equally)•A gene from each parent•Carrying beta thalassemia HB disorder (minor beta thalassemia)•2 genes of Beta thalassemia life long disorder (major beta thalassemia)

SymbolismBeta Thalassemia

• Greek letter used to designate globin chain:

SymbolismBeta Thalassemia

+: Indicates diminished, but some production of globin chain by gene:

+

SymbolismBeta Thalassemia

0 :Indicates no production of globin chain by gene:

0

Classification & Terminology Beta Thalassemia

• Normal /• Minor /0

/+

• Intermedia 0/+

• Major 0/0

+/+

Beta Thalassemia Minor

• Carrying beta thalassemia beta thalassemia gene + normal HB A gene

Testing

• Measure RBC size (MCV).•Analyse the types of HB.•(A+A2)

Advantages• Protection from Malaria•Protection from heart attacks•But……………………?

Passing beta thalassemia minor

The child may carry beta tahassemiaThe child may not carry any HB variant

Beta thalassemia major• 2 defected Beta genes no beta chains synthesis alpha chains precipitate premature death of RBCs.•Complications•Enlargement…

Treatment• Regular Blood transfusion ……4 weeks.•Blood testing•Live through 20s ……remove iron (desferrioxamine) pump•Bone marrow transplantation•DisadvantagesExpensive , tiresome , not available for every one

The need of the hour (prevention)

•Screening and Counseling1. Carrier testing 2. Inform carriers3. Both carriers counsellor Prenatal diagnosis (unborn baby) if affected terminate or continue with planning Neonatal diagnosis (after birth) if early diagnosed Save the child

Telling a partner to have a blood test

When ?•Before marriage •Before pregnancy •As soon as the pregnancy started

•Easy….. because ?

Passing Beta thalassemia major

• Child may carry beta thalassemia major•Child may not carry any HB variant•Child may carry beta thalassemia trait

Facts•Beta thalassemia major one of the commonest inherited disorder•1 of 50 human beings carry beta thalassemia (100 million carriers)•100000 children are born with beta thalassemia major•Carriers are particularly common among people originate from Mediterranean , ME and east of Asia and not common among people from northern Europe.