We spent a lot of time talking about anaemia.
I just want to finish off by introducing the
other side of the coin where the patient has
too many red cells. In that, we call polycythaemia.
Here we see an increase in the haemoglobin
concentration. It makes the blood more difficult
to pump around the body, it is more viscous
and complications here include blood clots,
tiredness, lethargy and also pruritus or itching,
which is particularly seen in polycythaemia
vera. So I will explain in a minute. On the
right is a nice diagram to explain how to
diagnose polycythaemia. One of the common
problems that we encounter. On the left, we
see normal constituents of blood and red is
the red cell mass and in green is the plasma
volume and of course we are looking at the
haemoglobin concentration and it depends on
the relative amount of those, but on the left
is the normal range. In the middle is somebody
with primary polycythaemia that red cell masses
definitely increased as you can see above
the normal range that plasma volume remains
the same. But on the right is a condition
where the red cell mass has increased, but
actually remains below the normal range, but
here we have a reduction in the plasma volume.
So actually we think as polycythaemia because
the ratio is now normal although there is
not actually a true increase in the red cell
mass. So if somebody is terribly dehydrated,
you may see that sort of picture.
Let us look at how we classify polycythaemia.
Polycythaemia, as you will see on the left,
can be diagnosed, classified as either a primary
polycythaemia due to a myeloproliferative
disorder or secondary to an increase in erythropoietin.
Lung disease, smoking, altitude or sometimes
a tumour producing a lots of erythropoietin
and driving the bone marrow. And on the right
is quite a useful algorithm for approaching
patients who have potential polycythaemia.
You can see at the top the potential haematocrit
that might make you consider that the patient
has polycythaemia and male over 0.52 or female
over 0.48. Going down, you can check whether
the red cell mass is truly raised or if not,
it is an apparent polycythaemia. It the red
cell mass is raised or they cause of secondary
polycythaemia present. If that is true, it
can be a secondary polycythaemia and if not
consider polycythaemia vera. Now the management
of polycythaemia vera depends on the genetic
abnormality of this disorder which we now
understand. Almost every patient has a mutation
in the JAK2 gene and we can use this to introduce
nutrients as well as taking off blood or using
drug such as hydroxycarbamide JAK2 inhibitors,
which are all tablets are now being used in
this disorder and I will talk more about that
in the lecture on myeloproliferative diseases.
Secondary polycythemia is best treated by
correcting the underlying cause stopping the
patients smoking, trying to treat the lung
disease, which can you, use phlebotomy taking
off blood donations if you need to.
So In summary, I hope you have seen from the
slides that disorders of the red cell are
very common within the world. The management
of anaemia is dependent on making an accurate
diagnosis of the etiology based on targeted
treatment, but an excess of red cells can
also be dangerous and is just important that
we get the diagnosis right in those cases.
Thank you very much for watching the lecture.