Biochemistry

Question 1

What types of anaemias are there?

Answer 1

• Haematinic deficiency
• Normochromic/normocytic anaemia
• Marrow syndrome
• Iron deficiency
• B12 deficiency
• Folate deficiency
• Secondary anaemia
• Aplastic anaemia
• Malignancies
• Haemolytic anaemias

Question 2

What are congenital anaemias?

Answer 2

• RBC membrane (hereditary elliptocytosis, hereditary spherocytosis)
• RBC enzyme deficiencies (G6PD, pyruvate kinase)
• RBC haemoglobin disorders (thalassaemias, sickle cell disease)

Question 3

What are acquired anaemias?

Answer 3

• Autoimmune haemolysis (AIHA)
• Fragmentary haemolysis (HUS, TTP, Waring Blender Syndrome)
• Drugs, infections, toxins
• Copper Deficiency (Wilson’s disease)

Question 4

What is the role of transcobalamin 1?

Answer 4

Transcobalamin 1 (TCN1) or hepatocorrin is a glycoprotein produced from salivary glands and it protects cobalamin (vit B12) from acid degradation in the stomach by producing hepatocorrin-vitB12 complex.

Question 5

What happens to B12 in the duodenum?

Answer 5

Once in the more neutral duodenum pancreatic proteases degrade hepatocorrin, releasing free cobalamin (i.e. free B12), which now binds to intrinsic factor (IF) for absorption by the enterocytes of the terminal ileum.

Question 6

How is B12 taken into the circulation?

Answer 6

B12-IF complex is taken up into circulation by cubulin receptors through endocytosis-mediated absorption.

Question 7

What are the normochromic/normocytic anaemias?

Answer 7

1. Acute blood loss
2. Anaemia of chronic disease or secondary anaemia
3. Anaemia of renal failure - deficiency of erythropoiertin

Question 8

What causes microcytic anaemias?

Answer 8

Anything that reduces the production of Hb inside the developing erythrocyte will tend to encourage more cell divisions than normal (iron deficiency, thalassaemia) and the erythrocyte will become smaller.

Question 9

What causes macrocytic anaemia?

Answer 9

Anything that delays nuclear development e.g. reduced DNA synthesis (B12, folate deficiencies, chemotherapy) will tend to mean fewer cell divisions will take place before the final MCH is attained and the red cells tend to be larger.
- Alcohol

Question 10

What are hypochromic microcytic anaemias?

Answer 10

• Iron deficiency
• Sideroblastic anaemia (congenital)
• Thalassaemias

Question 11

What are the types of macrocytic anaemia?

Answer 11

• B12
• Folate
• Alcohol

Question 12

What is iron deficiency anaemia?

Answer 12

• Inadequate iron-containing foods in the diet
• Malabsorption (coeliac disease, milk, tea)
• Blood loss - especially from GI tract

Question 13

Describe thalassaemia

Answer 13

Beta thalassaemia trait - a carrier or minor disease has raised HbA2
Beta thalassaemia major - no HbA, just HbF

Question 14

What are the causes of iron deficiency anaemia?

Answer 14

• Physiological - rapid growth, menarche, pregnancy
• Neonatal - premature, low weight, blood loss
• Diet e.g. vegetarian
• GIT - NSAIDs, colonic or gastric cancer
• Pre-menopause - menorrhagia
• Miscellaneous - renal tract bleeding, bleeding diathesis

Question 15

What is B12 or folate deficiency?

Answer 15

Cause megaloblastic anaemia - high MCV

Question 16

What causes vit B12 deficiency?

Answer 16

• Pernicious anaemia (autoimmune disorder resulting in reduced production of intrinsic factor)
• Drugs e.g. metformin, PPIs, NO
• Gastric - gastrectomy, Zollinger-Ellison syndrome
• Inherited - Imerslund Grasback syndrome
• Intestinal - malabsorption, Crohn’s
• Nutritional - malnutrition, vegan diet

Question 17

What causes folate deficiency?

Answer 17

• Drugs - alcohol, methotrexate, trimethoprim, anticonvulsants
• Excessive requirements in pregnancy, malignancy, blood disorders or malabsorption
• Excessive urinary excretion
• Liver disease