Deficiencies in Red Cell production

Question 1

What are some causes of abnormal erythropoiesis

Answer 1

Exposure of bone marrow to chemicals; benzene, chemotherapy, parvovirus infection, autoimmunity

Chronic kidney disease where EPO production is insufficeint to stimulate normal levels of erythropoiesis

Question 2

Name some causes of reduced erythropoiesis

Answer 2

Lack of response to haemostatic loop so insufficient EPO production

Empty bone marrow unable to respond to EPO

Reduction of normal haemopoietic cells due to infiltration of marrow by cancer cells of fibrous tissue

Question 3

Name and briefly describe causes of abnormal haemoglobin synthesis

Answer 3

Iron deficiency anaemia - iron supply inadequate for requirements

Anaemia of chronic disease

Globin gene mutation - mutation or deletion of globin protein genes (thalassaemia or sickle cell)

Deficiencies in building blocks for DNA synthesis - Vit B12 or folate deficiency

Question 4

How do B12 and folate deficiency cause anaemia and what sort of anaemia is it

Answer 4

Megaloblastic anaemia

B12 and folate required for DNA synthesis so deficiency means red cell precursors are unable to synthesise DNA and cannot divide. Nuclear maturation and cell division lag behind cytoplasm development so large red cell precursors are released into the bloodstream

Question 5

Where is folate absorbed and what happens to it when it is absorbed

Answer 5

Mainly in duodenum and jejunum

Intestinal cells convert it to tetrahydrofolate (FH₄)

Question 6

How can a folate deficiency occur

Answer 6

dietary deficiency - poor diet

increased use - pregnancy, increased erythropoiesis

disease of duodenum and jejunum

lack of methyTHF

Alcoholism

urinary loss in liver disease and heart failure

Question 7

How is Vitamin B12 absorbed

Answer 7

1. B12 forms a complex with haptocorrin in mouth
2. Haptocorrin B12 complex is then digested by pancreatic proteases in small intestine, releasing B12
3. B12 binds to intrinsic factor and this complex is absorbed in the terminal ilium
4. Once absorbed, B12 forms complex with transcobalamin II and is released into bloodstream

Question 8

What type of anaemia is caused by a lack of B12 absorption, what causes this

Answer 8

Pernicious anaemia caused by intrinsic factor deficiency

Question 9

What causes a Vit B12 deficiency

Answer 9

Dietary deficiency - poor diet, vegan diet

Lack of intrinsic factor - autoimmune disease affecting gastric parietal cells

Diseases of the ileum - Crohn’s disease

Lack of transcobalamin - congenital deficiency