Haematological disorders Flashcards
What is haemopoiesis?
The process which maintains lifelong production of haemopoietic (blood) cells
Where is the main site of haemopoiesis in the foetus and in postnatal life?
Fetal - fetal liver
Postnatal - bone marrow
How does HbF (fetal haemoglobin) differ from adult Hb?
HbF has a higher affinity for oxygen than adult Hb
When does HbF stop being present in the blood stream?
After about 1 year HbF is very low in healthy children
How does Hb alter throughout birth and the first stages of life?
Hb concentration is high at birth but falls to its lowest level at 2 months of age
What are the mechanisms of anaemia?
Reduced red cell production (iron deficiency) Increased red cell destruction (haemolysis) Blood loss (relatively uncommon in children)
What are the main causes of reduced red cell production?
Ineffective erythropoiesis (iron deficiency, folic acid deficiency, chronic inflammation (JIA), chronic renal failure) Red cell aplasia (complete absence of red cell production)
What are the main causes of increased red cell destruction?
Red cell membrane disorders
Red cell enzyme disorders
Haemoglobinopathies
Immune
What are the main causes of iron deficiency in children?
Inadequate intake
Malabsorption
Blood loss
How would you diagnose iron deficiency in children?
Microcytic, hypochromic anaemia
Low serum ferritin
If the bilirubin is raised in anaemia what does that tell you about the cause?
It is haemolysis as bilirubin is created from the break down of red blood cells
What are the main diseases causing haemolytic anaemia?
Sickle cell
Beta thalassaemia
G6PD deficiency
How do you manage iron deficiency?
Dietary advice
Supplementary oral iron for several months, a minimum 3 months after Hb has returned to normal
What are the disease consequences of haemolysis?
Anaemia
Hepatomegaly and splenomegaly
Increased blood levels of unconjugated bilirubin
Excess urinary urobilinogen
What are the diagnostic clues to haemolysis?
Raised reticulocyte count
Unconjugated bilirubinaemia and increased urinary urobilinogen
Abnormal appearance of the red cells on a blood film
Positive direct antiglobulin test
Increased red blood cell precursors in the bone marrow
What is G6PD deficiency?
G6PD is the rate-limiting enzyme in the pentose phosphate pathway and is essential for preventing oxidative damage to red cells. Those deficient are susceptible to oxidant-induced haemolysis
How is G6PD deficiency inherited?
It is X-linked so mainly affects males
How does G6PD deficiency present?
Neonatal jaundice within first 3 days
Acute haemolysis precipitated by infection, certain drugs, fava beans and naphthalene in mothballs.
Fever, malaise and dark urine
How do you diagnose G6PD deficiency?
Measuring G6PD activity in red blood cells
How do you manage G6PD deficiency?
The parents should be given advice about the signs of acute haemolysis and provided with a list of drugs, foods and chemicals to avoid
What are haemoglobinopathies?
RBC disorders which cause haemolytic anaemia because of reduced or absent production of HbA (thalassaemia) or because of the production of abnormal Hb (sickle cell)
Which races is sickle cell most common in?
Patients whose parents are black and originate from tropical Africa or the Caribbean but it is also found in the middle east
How does sickle cell disease affect the cell shape?
HbS polymerises within RBCs forming rigid tubular spiral bodies which deform the red cells into a sickle shape.
What does the abnormal sickle cell shape mean practically?
The cells have a reduced lifespan and may be trapped in the microcirculation, resulting in blood vessel occlusion and therefore ischaemia in an organ or bone.
What exacerbates vaso-occlusive crises in sickle cell?
Low oxygen tension, dehydration, undue stress, excessive exercise and cold
What are the clinical features of sickle cell disease?
Anaemia Infection Painful crises Acute anaemia Priapism Splenomegaly Long-term problems