Microcytic anaemia Flashcards
Define microcytic anaemia.
Anaemia associated with a low MCV (<80fl)
What is the aetiology of microcytic anaemia?
- Iron deficiency (commonest cause) - blood loss e.g. GI disease, urogenital tract and hookworm infection.
- Anaemia of chronic disease - often normocytic bt may be microcytic
- Thalassaemia
- Sideroblastic anaemia
- Lead posioning
What are the causes of iron deficiency?
- reduced absorption - small bowel disease, post-gastrectomy
- increased demand - growth, pregnancy
- reduced intake - vegans
What is 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 haem synthesis.
What are some causes of anaemia of chronic disease?
- Chronic inflammatory disease
- Chronic autoimmune disease
- Chronic infections e.g. TB or infective endocarditis
- Malignancy
- Chronic renal failure
Serum ferritin is normal or raised
It may be caused by reduced RBC survival, reduced EPO response to anaemia, reduced iron release from BM to erythroblasts
Treat the underlying condition.
How common is iron deficiency anaemia?
- Commonest form of anaemia worldwide
- Affects 2-5% of adult men and post-menopausal women
- Commonest cause of anaemia in pregnancy
What are the signs and symptoms of iron deficiency anaemia?
- Non specific - tiredness, lethargy, malaise, dyspnoea, pallor, exacerbation of pre-existing angina/intermittent claudication.
- Lead poisoning symptoms - anorexia, nausea, vomiting, abdo pain, constipation, peripheral nerve lesions
Signs:
- Signs of anaemia - pallor, brittle nails and hair, koilonychia, leukonychia
- Glossitis - atrophy of tongue papillae
- Cheilitis - angular stomatitis
- Plummer-Vinson syndrome - dysphagia and glossitis
- Signs of thalassaemia
- Lead poisoning signs - blue gumline, wrist/foot drop, encephalopathy, convulsions, reduced consciousness
Summarise iron metabolism.
- Ferritin – stored iron form in cells
- Ferroportin – channel through which iron moves to leave basal membrane of cell
- Transferrin – molecule which transports iron in plasma
- Iron binding capacity is high in anaemia – a lot of transferrin is present in blood. TIBC is raised as not much is bound.
Ferritin is low if serum transferrin is also low because you wouldn’t store ferritin if you didn’t have enough Fe in plasma.
What are the blood film findings in
- iron deficiency anaemia ?
- sideroblastic anaemia ?
- lead poisoning ?
Iron deficiency - mirocytic, hypochromic (central pallor >one third), anisocytosis (variable cell size), poikilocytosis (variable sizes)
Sideroblastic anaemia - dimorphic blood film with population of hypochromic microcytic cells
Lead poisoning - basilophilic stippling (coarse dots represent condensed RNA in the cytoplasm)
What investigations would you do for microcytic anaemia?
Bloods:
- FBC - low Hb, low MCV, reticulocytes
- Serum iron - low in iron deficiency
- Iron binding capacity - TIBC raised in iron deficiency
- Serum ferritin - reduced in Fe deficiency
- Serum lead - if poisoning suspected.
Blood film
Hb electrophoresis - for Hb variants or thalassaemia.
- Sideroblastic - ring sideroblasts in bone marrow as iron is deposited in perinuclear mitochondria of erythroblasts which stains blue-green with Perl’s stain
If Fe deficiency anaemia in >50yr old OR post-menopausal women: upper Gi endoscopy, colonoscopy, haematuria ix if no obvious cause of blood loss.
How do you manage iron deficiency anaemia?
- Oral iron supplements - 200mg ferrous sulfate tablets containing 65mg of elemental iron BD or TDS with food.
- If intolerance or malabsorption, consider parenteral iron supplements (beware of risk of anaphylaxis)
- Monitor Hb and MCV: aim for rise of 1g/dL/week (monitor every 2-4 weeks)
- Refer to specialist if rise is <2g/dL after 2-4 weeks
NB: normal Hb in those units is 12g/dL/13 in men
How do you manage sideroblastic anaemia?
- Treat the cause (e.g. stop causative drug)
- Pyridoxine can be used in inherited forms
- If no response consider blood transfusion and iron chelation
How do you manage lead poisoning (causing anaemia)?
- Remove source
- Dimercaprol
- D-penicillamine
- Ca2+ EDTA
What are the complications of microcytic anaemia? What is the prognosis?
Complications:
- High-output cardiac failure
- Complications of cause
Prognosis - depends on cause
What are some common side-effects of iron supplementation?
- Constipation
- Black stools
- Diarrhoea
- Heartburn
- Nausea
- Abdominal/epigastric pain
