Anaemia (iron deficiency)

Question 1

List some DDx for a presentation of:

• bright red PR bleed with constipation and tenesmus
• fatigue
• weight loss
• PR non-tender mass

Answer 1

PDx. Iron deficiency anaemia secondary to CRC lesion bleed

DDx.
• Neoplastic- CRC, large polyp, GIT lymphoma, carcinoid tumour (neuroendocrine), prostate ca
• Vascular- angiodysplasia, ischaemic bowel (post emboli or shock)
• Inflammatory- UC, diverticular disease
• Mechanical- diverticulosis (mucosal out pouching due to muscle weakness)
• Anal disease- haemarrhoids, anal fissue, anal fistula
• Infection- gastroenteritis

Question 2

What is microcytic anaemia? Give some examples?

Answer 2

Microcytic anaemia (<800fL)
Path: decreased Hb production -> RBC divides further to maintain Hb concentration
• Anaemia of chronic disease (normocytic then microcytic)
• Iron deficiency anaemia
• Sideroblastic anaemia
• Thalassaemia
• Lead poisoning

Question 3

What is anaemia of chronic disease?

Answer 3

Anaemia of chronic disease
Path:
o Chronic disease -> acute phase reactants (hepcidin) by liver -> inhibits ferroportin (iron export channels)
-> Sequesters iron in storage sites of endothelial cells (aim to hide Fe from bacteria)
-> limits Fe transfer from macrophages to erythroid precursors
o Prevents enterocytes in gut from allowing iron into hepatic portal system -> reduces dietary absorption
o Suppresses EPO production -> decreased BM drive to produced RBCs

Question 4

What changes would you see in an iron study for anaemia of chronic disease?

Answer 4

• During disease, iron stored as ferritin to protect it from bacterial use
• High ferritin, low TIBC- ferritin rises (increased stores of Fe that cannot be used), TIBC decreased (less Fe needs to be obtained for storage)
• Low serum Fe, low % saturation- bone marrow will use Fe to make haem, cannot access stored Fe

Question 5

What is iron deficiency anaemia?

Answer 5

Iron deficiency anaemia
Path: blood loss OR dietary lack of iron
-> decreased iron available to for haem
-> decreased Hb formation
-> increased division (to maintain Hb conc) -> microcytic anaemia

Question 6

What changes would you see in an iron study for iron deficiency anaemia?

Answer 6

• Low ferritin, high TIBC – Fe stores used to make haem (low ferritin), liver produces more transferrin to obtain for Fe for storage (high TIBC)
• Low serum Fe, low % saturation- serum Fe depleted next after stores of Fe, saturation % decrease as less Fe bound to transferrin

Question 7

What is macrocytic anaemia? Give some examples?

Answer 7

Macrocytic (>100fL)- anaemia where RBCs are larger than normal (80-100)
• Megaloblastic (impaired DNA synthesis)
o Folate deficiency
o Vit B12 deficiency
• Non-megaloblastic (DNA synthesis not impaired)
o Diamond-Blackfan anaemia

Question 8

What is normocytic anaemia? Give some examples?

Answer 8

Normocytic anaemia- anaemia (low RBCs) where RBCs are of normal size (80-100fL)

Non-haemolytic:
o Anaemia of chronic disease (can become microcytic)
o Aplastic anaemia

Haemolytic:
o Intrinsic haemolytic 
- Hereditary spherocytosis
- G6PH deficiency
- Pyruvate kinase deficiency
- Paroxysmal noctural haemoglobuinuria 
- Sickle cell anaemia
- HbC disease
o Extrinsic haemolytic 
- Autoimmune haemolytic anaemia (AIHA)
- Microangiopathic anaemia
- Macroangiopathic anaemia

Question 9

What investigations would you order for suspected anaemia?

Answer 9

• FBC- low RBCs (EPO suppression reduces BM production)
• Iron studies
o Total iron binding capacity (TIBC)- how much tranferrin molecules present in blood
o Serum Fe- all serum Fe (not just in RBCs), limited use alone
o Transferrin- iron transport
o % saturation (ferritin)- % transferrin with iron bound to them, best serum marker for iron overload
• Blood smear
- anaemia chronic disease (normocytic then microcytic)
- Sideroblastic (sideroblasts: ring of Fe-laden mitochondria around nucleus)
- thalassaemia (microcytic, hypochromic, and target cells)
• Serum vit B6- sideroblastic anaemia
• Electrophoresis- thalassaemia