Haematology Flashcards
Foetal haemoglobin is comprised of what subunits?
2 alpha and 2 gamma subunits
Why is it important for foetal haemoglobin to have a higher affinity for oxygen than the maternal adult haemoglobin?
Foetal Haemoglobin needs to “steal” or displace oxygen from the mother’s Haemoglobin in the placenta
On an Oxygen dissociation curve, what is the x and y axis?
X axis: Partial pressure of O2
Y axis: Saturation of Hb with O2
What does it mean when the O2 dissociation curve of Foetal Hb is shifted to the left compared to Adult Hb?
It means Adult Hb requires a higher partial pressure of oxygen for molecule to bind to oxygen compared to Foetal Hb
When does HbF decrease in babies?
Production decreases from 32-36 weeks gestation, and at the same time HbA increases. By 6 months, very little HbF is produced
What is the mutation for SCD?
V600E mutation on position 6 of the beta-globin chain, of Adult Haemoglobin
Why does sickle cell disease not cause sickling of foetal Hb?
Because SCD affects the beta globin chain of Adult Hb, and in Foetal Hb there is only 2 alpha and 2 gamma chains
What medication can be used to increase production of Foetal Haemoglobin in patients with SCD?
Hydroxycarbamide
What factors cause the O2 dissociation curve to shift to the left?
Carbon monoxide
Foetal haemoglobin
What factors cause the O2 dissociation curve to shift to the right?
Increase in pCO2
Increase in temperature
Increase in 2,3 DPG
Decrease in pH (acidic)
What is Physiological Anaemia in Infancy?
When does it occur?
- Caused by negative feedback to EPO and suppression of Hb production
- Most common cause of anaemia in infancy
- Normal dip of Hb at 6-9 weeks
Why might anaemia of Prematurity occur? Several reasons
- Less time in utero
- RBC creation cannot keep up with rapid growth
- Reduced EPO levels
- Blood tests may remove circulating volume
What are some causes of anaemia in young babies?
- Physiologic anaemia of Infancy
- Anaemia of Prematurity
- Blood loss
- Twin to twin transfusion
- Haemolysis (HND, HS, G6PD deficiency)
What are two common causes of anaemia in older children?
- Iron deficiency anaemia, 2ndary to dietary insufficiency
- Blood loss, most commonly in menstruating women
What is the most common cause of blood loss causing anaemia in developing countries for older children?
How is it treated?
Helminth infection, with roundworms, hookworms or whipworms
One off dose -> Albendazole, Mebendazole
Anaemias can be categorised based on RBC MCV. What are causes of Microcytic anaemia?
TAILS mnemonic
- Thalassemia
- Anaemia of chronic disease
- Iron deficiency anaemia
- Lead poisoning
- Sideroblastic anaemia
Anaemias can be categorised based on a RBC MCV. What are causes of Normocytic anaemia?
3 A’s and 2 H’s
- Acute blood loss
- Anaemia of chronic disease
- Aplastic anaemia
- Haemolytic anaemia
- Hypothyroidism
Anaemias can be categorised based on a RBC MCV. What are causes of Macrocytic anaemia?
Macrocytic Megaloblastic:
- B12 deficiency
- Folate deficiency
Macrocytic Normoblastic:
- Alcohol
- Reticulocytosis
- Hypothyroidism
- Liver disease
- Drugs i.e. Azathioprine
What is a sign specific to haemolytic anaemia?
Jaundice
What are signs and symptoms specific to iron deficiency anaemia?
Signs:
- Koilonychia
- Angular cheilitis
- Glossitis
- Post cricoid webs
- Brittle hair & nails
Symptoms
- Pica
- Hair loss
Top 3 causes of iron deficiency anaemia?
- Dietary insufficiency
- Loss of iron (i.e. due to menstruation)
- Chronic conditions (i.e. Crohn’s)
Where is iron mainly absorbed in the gut?
In the duodenum and the jejunum
Why might some medications interfere with iron absorption? Give an example of a medication?
What else can interfere with iron absorption?
Iron requires stomach acid to keep iron in the soluble Fe2+ form. If there is less acid, Fe2+ -> Fe3+. Some medications like PPIs reduce stomach acid and thus interfere with iron absorption
Diseases like Crohn’s Disease and Coeliacs may also interfere with iron absorption
What is heme iron and non-heme iron?
Heme iron: Fe2+, aka ferrous
Non-heme iron: Fe3+, aka ferric
Outline how iron is transported in duodenal cells and in the blood?
In duodenal cells, iron is transported as Fe2+, bound to Ferritin. When in blood being transported, iron is carried as Fe3+, bound to Transferrin. Once it is deposited into cells, it is deposited back as Fe2+ bound to Ferritin
What is Total Iron Binding Capacity (TIBC)? Why is TIBC important?
TIBC refers to the total space on a transferrin molecule for iron to bind. TIBC is a good indicator for amount of Transferrin in blood
What is the equation for Transferrin Saturation?
Serum Iron / Total Iron Binding Capacity
What does:
- Low Ferritin mean?
- Normal Ferritin mean?
- High Ferritin mean?
- Low Ferritin: Iron deficiency anaemia
- Normal Ferritin: May still be iron deficient
- High Ferritin: Difficult to interpret, can be due to inflammation or iron overload
What does:
- High TIBC / Transferrin mean?
- Low TIBC / Transferrin mean?
- High: Iron deficiency
- Low: Iron overload
In Iron deficiency, what will the values be for TIBC, Transferrin, Transferrin saturation, and Ferritin?
TIBC: High
Transferrin: High
Transferrin saturation: Low
Ferritin: Low
What are the investigations for Iron deficiency anaemia?
- Full Blood Count: Hypochromic, microcytic anaemia
- Serum Ferritin: Low
- TIBC / Transferrin: High
- Blood film: Anisopolkiocytosis
- Endoscopy: Rule out malignancy
What is the management for Iron deficiency anaemia?
- Treat underlying cause
- Oral ferrous sulphate for 3 months
- Iron rich diet
- Transfusions (rare)
