Dr.Abdolreza Afrasiabi

Thalassemia & Heamophilia Genetic Reaserch Center

Shiraz Medical University

Hemoglobin tetramer

http://en.wikipedia.org/wiki/Image:Hemoglobin.jpg

Hemoglobin Structure %

A1 α2 β2 94-97%

A2 α2 δ2 2.5%

A1C α2 (β-N-glucose) 3%

F α2 γ2

There are 3 main categories of inherited Hemoglobin abnormalities:

Structural or qualitative: Genetic mutation involving amino acid deletions or substitution .(Hemoglobinopathy).

Quantitative: Production of one or more globin chains is

reduced or absent (Thalassemia).(HPFH): Hereditary persistence of Fetal Hemoglobin.

Complete or partial failure of γ globin to switch to βglobin.

Heterogenous group of disorders due to an imbalance of α and β globin chain synthesis

α thalssemia: α-globin chain production decreased

β thalassemia: β globin chain production decreased

Quantitative deficiency:

0 thalassemia: No β -globin chain is made

β + thalassemia: decreased b-globin chain is made

Beta () thalassemia:

- The disease manifests itself when the switch from to chain synthesis occurs several months after birth

- There may be a compensatory increase in and chain synthesis resulting in increased levels of Hb-F and A2.

- The genetic background of thalassemia is heterogenous and may be roughly divided into two types:

0 in which there is complete absence of chain production. This is common in the Mediterranean.

+ in which there is a partial block in chain synthesis. At least three different mutant genes are involved:

+1 – 10% of normal chain synthesis occurs

+2 – 50% of normal chain synthesis occurs

+3 - > 50% of normal chain synthesis occurs

Lab findings include:

Prepheral Smear

- hypochromic, microcytic anemia

- marked anisocytosis and poikilocytosis

- schistocytes, ovalocytes, and target cells

- basophilic stippling from chain precipitation

- increased reticulocytes and nucleated RBCs

chronic hemolysis leads to increased bilirubin and gallstones

hemoglobin electrophoresis shows increased Hb-F, variable

amounts of Hb A2, and no to very little A.

β-Thalassemia minor

Test to identify HbS.

HbS is relatively insoluble compared to other Hemoglobins.

Add reducing agent

HbS will precipitate forming and opaque solution compared with the clear pink solution seen in HbS is not present.

Solubility test (Sickledex):

Alpha () thalassemia

The disease is manifested immediately at birth

There are normally four alpha chains, so there is a great

variety in the severity of the disease.

At birth there are excess chains and later there are excess

chains. These form stable, nonfunctional tetramers that

precipitate as the RBCs age leading to decreased RBC

survival.

The disease is usually due to deletions of the gene and

occasionally to a functionally abnormal gene.

I. Silent carrier state

II. Alpha thalassemia trait

III. Hemoglobin H –disease

IV. Hemoglobin H –constant spring

V. Homozygous constant spring

VI. Hydrops fetalis

Lack of alpha protein is so small

Generally causes no health problems

Diagnosed when individuals has a child with Hb-H

or alpha thalassemia trait

Hb constant spring is an unusual form of it and

caused by mutation of alpha-globin with no health

problems

Reduced MCV and MCH with normal Hb A2 in

lab data

Physicians often mistake with iron deficiency

anemia

Created by the remaining beta globin

Lack of alpha protein is great enough to cause sever

anemia and health problems such as an enlarged

spleen, bone deformities, and fatigue

One parent is constant spring carrier and other

carrier of alpha thalassemia trait

Affected individual have a more sever anemia and

suffer more frequently from enlargement of the

spleen and viral infections

When two constant spring carriers pass their genes

on to their child .

The condition is less sever than Hb H-constant

spring and more similar to Hb-H disease.

There are no alpha gene in the individual’s DNA

Gamma globins produced by the fetus to form an abnormal Hb called Hb Barts.

Most individuals die before or shortly after birth

Co inheritance with heterozygous beta-thal and alpha-thal in particualr -alpha/-alpha genotype may be normalize MCV and MCH while Hb A2 levels remain elevated .

Interaction of delta-thal and beta-thal trait may reduce Hb A2 to borderline or normal level while MCV and MCH are reduced. phenotype of delta-beta-thal is similar to alpha but alpha/beta globin chain synthesis is 1.2 in delta-beta carrier.

1) Megaloblastic Anemia due to B12/Folic Acid deficiency

2) Liver disease (Lipid Metabolism)

3) Unstable Hb , Sickle Trait , S/B, S/a

4)hyper Thyroedism

5) Viral Treatment in Acquired immune deficiency HIV

6) Combined a/B with Normal index

1) Delta Beta Thalassemia (Hetero/Homo)

2)Hb H disease

3) Unstable Hb , Sickle Trait , S/B, S/a

5) Iron deficiency

6)Hb D

1) Hb A´2 –Hb G in S window in HPLC or Capillary System

a) Mutation in Delta gene (16 Gly Arg)

With increased Hb F

Parental Options

Procurement

removal of AF transabdominally with US* at 14-16 weeks

gestation determined via last menstrual period (LMP)

*Ultrasound (US):

locates the placenta (anterior or fundal in 70%)

assess amount of AF

date pregnancy via BPD, femur length, chest size

locate fetus

assess anatomy (brain, spinal cord, stomach, kidneys, HR)

Procurement (cont)

removal of 10-20 cc fluid which contains amniocytes

and fluid

use 20-21 gauge spinal needle, strict asepsis w/ or w/o

local anesthetic

AF is produced by the fetus

amniocytes are fetal in origin: skin, amnion, eyes, GU

tract, GIT, respiratory system

Risks1-3% overall for experienced docFetus:

infection (

Problems/complications

cannot do AFP for NTD; must do MSAFP at 15+ weeks

mosaicism

Rh

limb defects

Greatest advantage

TIME