Many of us have heard of blood group ABO and whether we are positive or negative for an antigen which is part of the Rh blood group system. I am A positive for example.
These are very clinically significant blood groups but did you know that there are a multitude of other blood group systems and antigens most of which you will never have heard of. They are however very important in blood transfusions and pregnancy.
In pregnancy, an investigation performed by Blood Transfusion laboratories is to identify whether a mother's immune system has been sensitised and created antibodies against one of these blood group antigens on their baby's red blood cells. If this is the case the antibody level needs to be monitored and assessment made regarding how much damage it could cause to the baby and how to manage this.
I haven’t seen a blood film like this on a neonate for a
long time, but here is one that presented recently on my weekend shift.
Haemolytic Disease of the Fetus or Newborn or HDFN for short.
The only clinical details I received were jaundiced since
birth and hence the reason for my decision to make a blood film.
In a normal neonatal film you would expect to see features
of the the organs being immature such as occasional echinocytes (spikey red cells reflecting kidneys), Howell-jolly bodies (a bit of DNA left in the red cell, suggesting an immature spleen), target cells (red cells that look like ..well a target...reflecting liver immaturity). The red cells are
far bigger than an adults and occasional fragments, polychromasia and nucleated red cells are normal. Very occasional spherocytes may also be seen.
Look at this film however, marked spherocytosis (the very dense dark damaged red cells), increased polychromasia ( purple staining young red cells) and increased nucleated red cells (very immature red cells normally seen in the bone marrow). This is not in any way normal for a neonate and my immediate thought was haemolysis.
So the key word here from a morphological perspective is 'marked' as opposed to occasional. Neonatal films can be tricky but it is not normal to have 'marked' numbers of anything.
It worth noting that neonates do not always
present in the same way as adults morphologically with haemolysis, and if a blood film
shows a dominate poikilocyte or bizarre shaped red cells it is worth
considering.
It is also good to remember that premature babies will often have an increase in red cell fragments and morphological signs that their organs are more immature.
Looking at the blood transfusion records the mother had an
anti-c antibody. This is likely to have developed during a previous pregnancy.
The baby here had the c antigen on it’s red cells and the mother’s immune
system was therefore sensitised and primed to destroy the foreign antigen. This
in effect means the mothers immune system was destroying the babies red cells!
The DAT was strongly positive which supports this.
This rapid destruction of red blood cells can cause an enlargement of the baby’s
liver and spleen which quickly try and compensate by making more red blood
cells. In severe cases the baby cannot cope with anaemia and heart failure
occurs before birth.
After birth build up of bilirubin can lead to liver enlargement and brain damage. The billribun here was very raised at 289 umol/L which required phototherapy to try and clear it.
I’ve been reading the following guidelines:
|
Article title: |
Blood Grouping and Antibody Testing in Pregnancy | British Society for
Haematology |
|
Website title: |
B-s-h.org.uk |
|
URL: |
https://b-s-h.org.uk/guidelines/guidelines/blood-grouping-and-antibody-testing-in-pregnancy/ |
Anti-D, anti-c and anti-K are the antibodies most often implicated
in destroying the babies red cells severely enough to need antenatal
intervention.
Clinically significant red cell antibodies should have their
concentration measured throughout pregnancy, in order to guide the management
and invervention in pregnancy before the antibody causes harm to the baby.
The guidelines suggest that Anti-D and anti-c are the only
antibodies currently quantified, whereas the other clinically significant
antibodies are titrated.
The mother in this instance initially had the anti-c
antibody at a very low level of 0.2 IU/ml. Three weeks later this had only
slightly increased to 0.5 IU/ml. Just
under a month later however the antibody level had risen to 10.6 IU/ml.
The table below taken from the BCSH guidelines indicates
that this level would give a moderate risk of haemolytic Disease of the Fetus
or Newborn.
The guidelines indicate that before 28 weeks anti-D and
anti-c should be serologically tested every 4 weeks, then every 2 weeks after
28 weeks until delivery.
An interesting case and as I said, one I haven't seen morphologically for some time. A number of laboratory disciplines were involved in this, demonstrating the importance of Pathology in every diagnosis.
