Iron balance is controlled mainly by absorption in the proximal small intestine, which compensates for iron loss.
Most iron is conveyed around the body bound to a protein called transferrin, which is metabolised so that iron can enter the cells. Any condition causing decreased absorption or increased loss can lead to iron deficiency anaemia.
The most frequent causes in adult males and menopausal women are gastrointestinal disorders, and in pre-meno-pausal women menorrhagia.
In the developing countries, the condition is seen in areas where meat is lacking from the diet.
The classic presenting symptom is fatigue and diminished capacity to undertake physical exertion. Clues that may lead one to suspect the diagnosis include dietary history (vegans, elderly patients with generally poor diet), reduced cognitive function (for example declining school performance), behavioural changes and haemorrhage from any orifice (menorrhagia, haematuria, haematemesis, haemoptysis and melaena).
Occasionally, the patient may present with dysphagia due to an oesophageal web, frequent infections or pica.
Early symptoms of iron deficiency, which may occur before frank anaemia develops, include pagophagia (the compulsive consumption of ice) and leg cramps.
The main physical sign is pallor of the mucous membranes, best seen in the internal surface of the lower eyelid. Other signs such as atrophic changes to the tongue and corner of the mouth are rarer in the western world. Prolonged severe iron deficiency can cause splenomegaly.
Further investigation of the cause will depend on the clinical picture. A full dietary history should be taken as, even in the developed world, food fads in the young and poor nutritional intake in the elderly can lead to reduced iron intake.
Gastrointestinal investigations, starting with endoscopy, should be arranged for any male or post-menopausal female with unexplained iron deficiency. Pre-menopausal women with menorrhagia will require appropriate gynaecological investigation.
Other causes of iron deficiency which are less frequent may need to be excluded, such as iron loss through the renal tract (persistent haematuria or haemoglobi nuria) or malabsorption (achlorhydria, proximal small bowel surgery, coeliac disease, sprue).
The differential diagnoses include hereditary spherocytosis, haemoglobinopathies, lead poisoning, sideroblastic anaemias and other causes of microcytic anaemia. The peripheral blood film may show hypochromic, microcytic cells and the platelet count may be raised, but these may be seen in other chronic anaemias.
The key diagnostic findings are a low serum iron and ferritin and a raised total iron binding capacity.
Bone marrow aspiration may be required in cases of diagnostic difficulty.
Tests to exclude other differential diagnoses, such as haemoglobin electrophoresis and tests for haemoglobin in urine and faeces, may be necessary.
Iron supplementation should be given while the underlying cause of the anaemia is investigated. Ferrous salts appear to be better absorbed than ferric salts and ferrous sulfate is the most regularly used preparation. Compound preparations which contain vitamin C and slow-release once-daily preparations do not appear to offer significant benefit.
The standard dose is 200mg (65mg elemental iron) three times daily for adults, less frequently if it is mild.
The main adverse effects are nausea, epigastric pain and altered bowel habit. Changing to another salt sometimes helps. Failing this, intramuscular iron hydroxide-dextran can be given. Patients should be given a small test dose to check for anaphylaxis.
Ferrous fumerate syrup is available for children, 2.5-5ml, given once or twice daily in children up to two years-old and 10ml twice daily in children aged between two and 18 years old.
Danger of iron poisoning
Dosage should be conservative, because iron poisoning in children is common.
The concentration of haemoglobin should rise by about 100-200mg/100ml per day or 2g/100ml over three or four weeks.
Treatment should be continued for three or four months after the haemoglobin has reached normal levels, in order to replenish iron stores.
The complications of prolonged iron deficiency include hypoxia, coronary insufficiency and ischaemic heart disease.
Atrophic gastritis and Plummer Vinson syndrome brittle nails and angular stomatitis may develop. Impaired immune function has been reported. In infants, growth restriction may occur, and neurological impairment may cause reduced IQ and behavioural problems.
Early recognition of iron deficiency is therefore important because it is easily treatable once the condition has been diagnosed.
In adults, providing the deficiency is not secondary to malignancy, the prognosis is excellent.
Dr Knott is a GP in Enfield, North London
- Frequent causes of iron deficiency in adult males and post-menopausal women are gastro-intestinal disorders.
- In pre-menopausal women, the main cause of iron deficiency is menorrhagia.
- Fatigue and diminished capacity for physical work are the key symptoms.
- Pallor of the mucous membranes is the key sign.
- Laboratory confirmation can be obtained by measuring serum iron, ferritin and total iron binding capacity.
- Consider gastrointestinal investigations and renal causes for patients with unexplained iron deficiency.
- The condition is rapidly reversible, but failure to recognise it can lead to long-term problems in adults and children.