Mother's Immune System Destroys Baby's Red Cells.

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.

A Medical Emergency

A case here that I wasn’t expecting to see on a recent weekend late shift, but a condition that is a medical emergency and fatal without the appropriate treatment, Thrombotic Thrombocytopenic Pupura or TTP for short.

This is a rare condition, and therefore even more important to keep in the forefront of the scientist’s mind when reviewing blood results. 

This patient attended Accident and Emergency, very unwell with a rash. The platelet count was 4 x10^9/l. The blood film was classic, severe thrombocytopenia with numerous fragments of red cells. This picture is consistent with  microangiopathic haemolysis.

Other significant markers are a raised bilirubin, LDH, Reticulocyte count , all markers of haemolysis and a raised creatinine, indicative of renal damage.

 

In this condition, clots are forming in blood vessels throughout the body, blocking oxygen flow to the body’s organs including  the brain, kidneys and heart, leading to complications such as stroke, myocardial infarction and renal failure.

The platelet count was so low because the platelets are being used up as the clots are forming, which will result in bleeding internally and under the skin. The red cell fragments are caused by red cells squeezing past blood clots, which leads to anaemia and a progressively falling haemoglobin. 

 For Scientists the action should involve

1. looking under the microcscope immediately on any new low platelet count. 

2. Note whether the haemoglobin is dropping aswell. 

3. The presence of red cell fragments, polychromasia and thrombocytopenia on a blood film is highly suggestive of a microangiopathic haemolytic anaemia which includes TTP and HUS. DIC also gives a similar picture. 

NOTE: even the very occasional red cell fragment is enough to consider this condition.

4. Add haemolysis markers on. We added a reticulocyte count, bilirubin and LDH. 

5.Phone the Consultant Haematologist and clinician immediately with all the relevant             information.

6. Further tedts of use are ADAMST13, Haptoglobin, clotting screen and D-Dimer.

The condition is caused by a lack of an enzyme called ADAMST13 that breaks down a clotting protein, Von Willebrand factor. This patient was indeed very deficient in ADAMST13. The cause of this to happen in this patient is unknown, but something had triggered the body to make antibodies against ADAMST13. A virus perhaps. In a separate case I was involved in a few years ago, a drinking binge in a young adult, triggered TTP!

The treatment for TTP is to exchange the plasma, giving back the ADAMST13 enzyme, which is a life saving treatment. Very sadly this patient didn't survive long enough to receive this treatment.

 This is a medical emergency with often only hours before life threatening and fatal complications occur, which unfortunately was the outcome in this case.

Hypogranular neutrophils picked up on an XN10 plot

This is a good example of how the differential plots must be reviewed when interpreting Full Blood Count results.

The X axis on the Sysmex XNs shows an increase in cell complexity from left to right ( i.e granules and nuclear lobulation). Eosinophils are therefore far right because of their heavy granulation and nuclear lobulation and neutrophils are just left of these.  The monocytes are to the left of the neutrophils as they are less complex , but higher up on the Y axis due to an increased DNA/ RNA content. Lymphocytes are far left.

Look at this plot. The neutrophil population is partly too far left illustrating that whatever these cells are, they are far less complex. My thinking was that there could be dysplasia, either dysplastic nuclei or hypogranular neutrophils which both make the neutrophils less complex and therefore appear left of the expected plot position.

The blood film did indeed show some hypogranular netrophils. Other neutrophils however showed toxic granulation The clinical details were bilary sepsis so features of infection/ inflammation would be consistent 

Reading up on the mechanism behind neutrophils lacking granules, it could be defective granule formation or excessive degranulation during development.

The significance of this feature could be that this is a myelodysplasia or myeloproliferative disorder. 

The Full Blood Count results were not remarkable and the film would not have been made if the plot wasn't viewed.  Therefore very important!

UK NEQAS Digital Morphology Instagram page

Just started following UK NEQAS Digital Morphology Instagram account. Take a look! https://www.instagram.com/haematography/

Digital Morphology case 2006DM

10th January 2021 Digital Morphology case 2006DM 

This was a good P.Vivax film showing different trophozoite stages and how the level of red cell distortion increases as the trophozoite matures. 

The initial phase, red cell enlarged but still round with cytoplasmic dots.

This is compared to  how a later trophozoite stage greatly distorts and enlarges red cells . It also highlights how later stages cause red cells to become pale as the parasite metabolises haemoglobin.

I found this very useful as I would typically associate P. Vivax with the second picture, a very amoeboid trophozoite and greatly distorted red cell. It is worth remembering how different the trophozoite can appear in all species, depending on it’s maturity. 

Circulating schizoints and gametocytes are often seen in this species, although not in this particular case. 

The case narrative also gives some useful links to training aids. I will be using these for Malaria speciation training. 

https://haematologyetc.co.uk/Malaria_stage_recognition https://haematologyetc.co.uk/Malaria_species_recognition

Survey 2004RD: Rapid Diagnostic Techniques for Malaria

Survey 2004RD: Rapid Diagnostic Techniques for Malaria Date 9/11/20 

The November 2020, RDT survey directs partcipants to read the Malaria rapid diagnostic test performance. Results of WHO product testing of malaria RDTs: round 8 (2016-2018). This can be found at https://www.who.int/malaria/publications/atoz/9789241514965/en/ 

The document gives an overview of findings from rounds 5-8 of Malaria RDT product testing. This is a good guide for laboratories on choosing an RDT kit that is likely to perform to a high a standard The document gives in detail how these RDT kits were evaluated. A simple summary is given in this flowchart.

Kits were assessed based on the following: -sensitivity, to detect nearly all clinically significant cases of malaria; - specificity, to accurately discriminate non-malarial febrile illness from malaria in order to ensure appropriate management and accurate disease monitoring; - stability, to maintain accuracy after transport and storage in ambient conditions; and - ease of use and adequate labelling and instructions for use to ensure safe, correct preparation and accurate interpretation of results.

The results are too extensive to document here, but I will be looking at my own laboratory kit and comparing it’s performance to others on the market, based on these findings.

A Rare One!

Quite a rare one here... I had to look it up! Pearson’s Syndrome.. it’s a Congenital Sideroblastic anaemia and Pancreatic dysfunction. I was trying to work out why this patient had macrocytic red cells and thrombocytopenia. Reading around this, it seems that these features are consistent with this form of sideroblastic anaemia. I usually associate sideroblastic anaemia with microcytes and dimorphic red cells and hadn’t appreciated that mainly macrocytes could be a feature and how many different types of sideroblastic anaemia there actually were. Reading about this, it seems that a good starting point in searching for the cause of sideroblastic anaemia is to look at the MCV. So MCV is important! Bottomley, S. Leung L. Tirnauer, JS. (2020) Causes and the Pathophysiology of the Sideroblastic Anaemias

I also saw these. Pappenheimer bodies, which are blue iron containing inclusions in the red cell, and often found near the edge , I usually scan for these when I have a patient with an unexplained anaemia and dimorphic red cells. A lot learnt today! I’ll be using this blood film in morphology training to demonstrate the diversity of red cell size in the Sideroblastic Anaemias.