Haemolytic anaemia Flashcards
(40 cards)
What is haemolytic anaemia?
A number of conditions that result in the premature destruction of RBCs.
Presents with acute or subacute development of fatigue or jaundice, and may include orthostasis and mild splenomegaly.
NB: Usually macrocytic anaemia, with↑reticulocyte count and jaundice with unconjugated hyperbilirubinaemia
What indicated haemolytic anaemia?
Anaemia, reticulocytosis, low haptoglobin, high LDH and high indirect bilirubin suggest haemolysis.
What does Coomb’s test do?
Differentiates immune from non-immune aetiologies.
Causes of haemolytic anaemia?
Hereditary-
Inherited RBCs defects (membrane)- hereditary spherocytosis, elliptocytosis (pyropoikilocytosis)
Enzyme deficiencies- G6PD deficiency, Pyruvate kinase deficiency.
Abnormal Hb production- sickle cell anaemia, thalassaemia
Acquired-
Immune- Autoimmune (warm or cold reacting antibodies, drug-induced, autoimmune)
Non-immune- infection, trauma (like malignant HTN), HELLP syndrome in pregnancy, mechanical prosthetic heart valves, march haemolysis, thermal injury and osmotic lysis, hypersplenism and liver disease.
Signs & symptoms of haemolytic anaemia?
Pallor Jaundice Fatigue Shortness of breath Dizziness Splenomegaly Active infections Episodic dark urine Triggered by exposure to cold
Risk factors of haemolytic anaemia
Autoimmune disorders Lymphoproliferative disorders Prosthetic heart valve Family origin in the Mediterranean Middle East Sub-Saharan Africa Southeast Asia FHx of haemoglobinopathy or RBC membrane defects Paroxysmal nocturnal haemoglobinuria Thermal injury
Tests and investigations of haemolytic anaemia
FBC (low Hb) MCHC (increased) Reticulocyte count Peripheral smear Unconjugated bilirubin LDH Haptoglobin Urinalysis Direct antiglobulin test (DAT or Coombs)
What is the Coombs test?
It tests for antibodies to RBCs.
There’s indirect and direct Coombs test.
What is the Indirect Coombs test?
This is the test used to cross match blood for suitability for transfusion.
A positive test means the tested donor red cells are incompatible and should not be given as a transfusion.
Blood sample from donor and recipient’s serum (containing antibodies), are obtained and mixed together.
Antihuman antibodies (Coombs reagent) are added to the mixture.
If RBCs agglutinate, the test is positive.
When is indirect Coombs test used?
Prenatal testing for pregnant women.
Testing blood prior to a transfusion.
What is the direct Coombs test?
This test is done much less often and detects
antibody to patient’s own serum causing an autoimmune haemolytic anaemia.
Blood sample from patient with immune-mediated haemolytic anaemia is washed to
extract RBCs.
RBCs incubated with antihuman antibodies (Coomb’s reagent).
If RBCs agglutinate, the test is positive
When is direct Coombs test used?
Used to identify haemolytic anaemia.
Differentials of haemolytic anaemia?
Anaemia due to blood loss
Underproduction anaemia
Transfusion reaction.
Management of haemolytic anaemia?
Once the diagnosis of haemolytic anaemia has been determined, a haematological
consultation is warranted.
All aetiologies of haemolytic anaemia require some degree of supportive care- supportive care includes transfusions and folate supplementation.
What is hereditary spherocytosis?
autosomal dominant, commonest inherited RBC disorder in northern Europeans.
RBCs are less deformable and get trapped in the spleen, causing extravascular haemolysis and splenomegaly.
Blood film shows micro-spherocytes and polychromatic macrocytes
(reticulocytes), with no areas of central pallor
Diagnosis of hereditary spherocytosis?
EMA-binding test is gold standard but if family history + blood film + FBC results correlate, it is not required.
Complications of hereditary spherocytosis
Neonatal and adult jaundice
Chronic haemolysis
Increased risk of gallstones from increased bilirubin
Management of hereditary spherocytosis?
Regular folic acid supplementation, often splenectomy required.
What is hereditary elliptocytosis?
Hereditary elliptocytosis
(pyropoikilocytosis) –autosomal dominant,
1:2000
incidence. Not clinically significant except in homozygotes
Also known as ovalocytosis.
In most cases treatment is not necessary.
In the most severe variants, folic acid, red cell transfusion and splenectomy (after the age of 5) may be required. Patients should be monitored during events known to precipitate haemolysis.
Pathophysiology of hereditary elliptocytosis?
a group of disorders of the red blood cell (RBC) membrane that are characterized by elliptical-shaped erythrocytes (elliptocytes) and shortened RBC survival.
Unlike normal RBCs, which repeatedly and momentarily assume an elliptical shape to negotiate through capillaries but then regain their biconcave discoid shape after they pass through the microcirculation, the RBCs in HE lack the elastic recoil necessary for returning to the discoid shape and eventually assume the fixed characteristic morphology of elliptocytes, with a decreased surface-to-volume ratio.
These elliptocytes are not as deformable as normal RBCs and are eventually trapped and removed by the spleen; this manifests as haemolytic anaemia.
What is hereditary stomacytosis?
Hereditary stomatocytosis is characterized by excessively water-laden erythrocytes.
The extremely high influx of Na+(sodium) and water from the plasma exceeds the loss of cellular K+ (potassium ion) and the resulting swollen red cells show a unique combination of large size (high mean corpuscular volume [MCV]), low mean corpuscular hemoglobin concentration (MCHC), and osmotic sensitivity in the osmotic fragility test.
No other condition shows this unique combination. Blood smears feature stomatocytes, or a mixture of stomatocytes and spherocytes.
What is G6PD deficiency?
X-linked recessive disease.
Blood film shows bite-cells
and blister-cells, after removal of Heinz bodies (denatured Hb) from RBCs.
May also show contracted RBCs.
What does G6PD deficiency precipitated by?
Precipitated by:
Drugs–aspirin, primaquine, sulphonamides, nitrofurantoin, vitamin K
Exposure – broad beans/favism, moth balls, henna
Infection
Diagnosis of G6PD deficiency
Enzyme assay for G6PD levels >8 weeks after crisis (as young RBCs may have enough enzyme so results normal)
