Now let's talk about thalassemia.
Thalassemia is an autosomal recessive blood
disorder that reduces the production of hemoglobin.
Patients with thalassemia do not make enough hemoglobin
which is the iron-containing protein in red blood cells
that carries oxygen to the
cells throughout the body.
When there isn't enough hemoglobin,
the body cells don't function properly
and the red blood cells die off quicker leaving
fewer healthy red blood cells in circulation.
There two ways to classify thalassemia, this is based
either on the alpha or beta type of hemoglobin affected
and it can also range in severity and this is
either the trait of minor, intermedia or major.
Symptoms usually appear in the first two years
of life and a life-threatening anemia can develop.
This is a common blood disorder worldwide, thousands
of them fence with beta thalassemia are born each year.
Beta-thalassemia occurs more frequently
in patients from the Mediterranean countries,
North Africa, the Middle East,
India, Central Asia and Southeast Asia
Here you can see the distribution of thalassemia
and sickle cell anemia and the overlap between them.
These are both familial
disorders passed genetically
so it makes sense that we see concentrations
of these disorders in certain regions
as a mutated genes continue to be
passed down through the generations.
Thalassemia major and thalassemia intermedia
are inherited in an autosomal recessive pattern
which means both copies of the HBB gene and each
cell must have the mutation to display the disease.
The HBB gene provides instructions for making the protein
called beta-globin which is a subunit of hemoglobin
The parents of an individual with an autosomal recessive
condition can each carry one copy of the mutated gene
but they typically don't show any signs and
symptoms of the condition, meaning they are carriers.
In regard to thalassemia, even
though it's a recessive disorder,
sometimes patients with only one HBB
gene and each so can develop a mild anemia.
And these mildly affected patients
are said to have thalassemia minor.
Here we see two parents who
are carriers for the thalassemia gene
meaning they have one defective
gene and one normal gene.
They are largely unaffected
but they can have a mild anemia.
With each pregnancy, you can see that their
offspring have a 25% chance of developing thalassemia
by receiving both mutated genes.
A 50% chance of being a carrier and being
asymptomatic or maybe having a mild anemia,
and a 25% chance of not having any mutated genes at
all and these patients will have normal hemoglobin.
Remember the odds reset with each pregnancy.
People with only one HBB
gene can develop a mild anemia.
This is important to remember, this thalassemia minor and a
child can receive a copy of these mutated genes from both parents
and then they would have
thalassemia major or intermedia.
Now let's talk about the pathology of thalassemia
by comparing normal and abnormal hemoglobin.
Here is a patient with normal hemoglobin.
There are no mutated genes to disrupt the hemoglobin
so there is a normal amount and it functions normally.
These patients do not have
thalassemia and they are not carriers.
In the centre you can see a single mutation.
This patient will be a carrier of beta
thalassemia trait also known as thalassemia minor
and again they're gonna have
hemoglobin but it's not going to have enough
and these patients
might have a slight anemia.
On the right, you'll see what happens
when a patient has two of the mutated genes
and this causes a severe
microcytic hypochromic anemia.
This patient is blood transfusion-dependent and if left
untreated they may develop splenomegaly and bone deformities.
This can progress to death before the age of 20.
So remember patients with
thalassemia lack functional hemoglobin.
The red blood cells do not develop normally.
There is a shortage of mature red blood cells and these
patients will develop a microcytic hypochromic anemia.