Iron-Deficiency Anaemia
Anaemia arising when iron intake or absorption fails to match losses or demand, so haemoglobin synthesis fails first and red cells emerge small and pale, and in an adult the default assumption is chronic blood loss until a source is found.
In a nutshell
Iron deficiency starves haemoglobin synthesis, producing microcytic hypochromic anaemia. In an adult with no physiological explanation, the mechanism demands a search for occult chronic blood loss, especially gastrointestinal malignancy.
Classic presentation
An older adult with insidious fatigue, breathlessness and pallor, microcytic anaemia on FBC, and no obvious source of blood loss on history.
Key points
- Microcytosis and hypochromia follow directly from inadequate haemoglobin packing during red cell maturation, not from too few precursors.
- The three mechanisms are loss, demand and malabsorption: every cause on the differential is an instance of one of these.
- Unexplained iron deficiency in a man or postmenopausal woman means find the bleed; gastrointestinal malignancy must be excluded via the 2-week-wait pathway.
- Ferritin is an acute-phase reactant and can be falsely normal in inflammation, so transferrin saturation adds information when ferritin is equivocal.
- Iron is needed by dividing epithelium as well as marrow, which is why glossitis, koilonychia and pica accompany the anaemia.
First-line investigation
FBC and blood film to demonstrate the microcytic hypochromic picture, followed by serum ferritin to confirm depleted iron stores.
First-line management
Oral iron replacement alongside a directed search for the underlying cause, with 2-week-wait endoscopy referral in men and postmenopausal women.
Exam traps
- Do not replace iron and discharge an older adult without investigating for a gastrointestinal source: the anaemia is a clue to the cancer, not just a lab abnormality to correct.
- A normal ferritin does not exclude iron deficiency if there is coexisting inflammation; interpret alongside transferrin saturation and the clinical picture.
- Microcytic anaemia is not always iron deficiency: thalassaemia trait and anaemia of chronic disease can mimic it, so confirm with iron studies before treating.
Educational content pending clinical review. Not medical advice.