Microcytic hypchromic anaemia
Iron deficiency anaemia
A fall in haemoglobin concentration secondary to depleted iron stores.
Causes of iron deficiency:
· Inadequate supply due to poor dietary intake (normal requirements 0.5–1 mg per day).
· Inadequate absorption, e.g. in coeliac disease or post-gastrectomy.
· Increased demand such as during growth or pregnancy.
· Increased loss from bleeding including occult gastrointestinal bleeding or menstruation.
Most of the iron within the body is circulating as haemoglobin. The remainder is stored in the bone marrow, hepatocytes and skeletal muscle cells. As an individual becomes iron deficient the bone marrow stores are depleted prior to the development of a microcytic anaemia.
Symptoms of anaemia include fatigue, faintness, headaches and breathlessness. In patients with known iron deficiency anaemia, it is important to enquire about dietary iron intake, history of blood in faeces, menorrhagia and a history of taking nonsteroidal anti-inflammatory drugs, aspirin or warfarin. On examination there may be pallor, tachycardia, cardiac failure and specific features of iron deficiency including glossitis, angular stomatitis and brittle spoon shaped nails (koilonychia). A rectal examination should be performed.
Full blood count demonstrates a microcytic (low MCV) hypochromic (low MCH, MCHC) anaemia. Blood film confirms small, pale staining (hypochromic) cells, variable shaped red blood cells (poikilo-cytosis) and variable sized red blood cells (anisocytosis). The white blood cells and platelets should be normal.
A low serum ferritin is the normal diagnostic investigation; however, it is falsely raised in liver disease and renal failure.
Other tests include a low serum iron and raised total iron binding capacity. Bone marrow aspiration is not usually required, but shows erythroid hyperplasia and a lack of iron stores on Perl’s staining.
Investigation of established iron deficiency may require faecal occult blood testing and upper or lower gastrointestinal endoscopy.
The underlying cause must be identified and treated where possible. Iron deficiency is treated with oral iron supplements, which should result in a rise of 1 g/dL of haemoglobin per week. Supplements are usually required for at least 6 months to replenish iron stores. Failure of response may be due to poor compliance, severe malabsorption, continued significant blood loss or another cause of anaemia. Rarely parenteral iron treatment may be required. In severely symptomatic anaemia, blood transfusion may be required; however, this may interfere with subsequent investigations.