microcytic anaemia

Question 1

definition

Answer 1

Anaemia associated with low MCV (<80 fl).

Question 2

causes

Answer 2

1. Iron-deficiency (commonest cause): Blood loss – e.g. gastrointestinal tract, urogenital tract, hookworm infection.
   - > OR reduced Absorption: Small bowel disease, Post-gastrectomy
   - > OR reduced intake: Vegans
   - > OR increased demand: Growth, Pregnancy.
2. Anaemia of chronic disease: Often normocytic but may be microcytic.
3. Thalassaemia

4. Sideroblastic anaemia: Abnormality of haem synthesis. Can be inherited (X-linked), or secondary to alcohol, drugs (e.g. isoniazid, chloramphenicol), lead, myelodysplasia. 
 Lead poisoning (e.g. in scrap metal or smelting workers): Interferes with globin and haemsynthesis.

Question 3

symptoms

Answer 3

Non-specific:

• Tiredness, lethargy, malaise, dyspnoea, pallor.
• Exacerbation of pre-existing angina or intermittent claudication

Lead poisoning: Anorexia, nausea, vomiting, abdominal pain, constipation, peripheral nerve lesions.

Question 4

signs

Answer 4

Signs of anaemia

• e.g. pallor of skin and mucous membranes.
• Brittle nails and hair.
• If long-standing and severe, koilonychia
• Glossitis: Atrophy of tongue papillae.
• Cheilitis: Angular stomatitis.

Lead poisoning: Blue gumline, peripheral nerve lesions (wrist or foot drop), encephalopathy, convulsions, reduced consciousness.

Question 5

investigations

Answer 5

• Blood: FBC (low Hb, low MCV, reticulocytes), serum iron (low in iron deficiency), iron-binding capacity (raised in iron deficiency), serum ferritin (low in iron deficiency), serum lead (if poisoning suspected).
• Blood film:
  Iron-deficiency anaemia: Microcytic (small), hypochromic (central pallor >one-third cell size), anisocytosis (variable cell size), poikilocytosis (variable cell shapes).
  Sideroblastic anaemia: Dimorphic blood film with a population of hypochromic microcytic cells.
  Lead poisoning: Basophilic stippling (coarse dots represent condensed RNA in the cytoplasm).
• Hb electrophoresis: For haemoglobin variants or thalassaemias.
  Sideroblastic anaemia: Ring sideroblasts in the bone marrow (iron deposited in perinuclear mitochondria of erythroblasts, stain blue–green with Perls’ stain).
• If iron-deficiency anaemia in >40 years and post-menopausal women: Upper GI endoscopy, colonoscopy and investigations for haematuria should be considered if no obvious cause of blood loss.

Question 6

treatment for iron deficiency anaemia

Answer 6

1. oral ferrous sulfate (iron replacement)
   ++ ascorbic acid (to help iron absorption)
2. IV iron dextran

if patient has symptomatic cardiac compromise:
+ red cell transfusion

Question 7

complications

Answer 7

High-output cardiac failure, complications of the cause.

Question 8

prognosis

Answer 8

depending on the cause