Like many things, low red cell count can be problem of production, loss or destruction.

So causes include:

• Bone marrow failure or infiltration (leukaemia, Fanconi’s, Blackfan Diamond, erythrovirus/parvovirus)
• Nose bleeds, gastrointestinal losses eg Meckel’s, gastritis, heavy periods
• Haemolysis eg G6PD deficiency, hypersplenism, autoimmune
• Iron, folate or B12 deficiency

In children, one of the most common causes is excessive milk consumption, which appears to lead to a low level colitis. Pica is often the presenting problem.

Investigations

• Blood film – Howell Jolly bodies if hypersplenism. Leucoerythroblastic reaction (with immature red cells, as well as immature white cells) can be due to malignancy but can also be due to infection and haemolysis. Spherocytes or other abnormal forms may suggest a hereditary haemolytic condition. Sickle cells in sickle cell disease.
• Low MCV suggests lack of iron, but may also be due to thalassaemia.
• Reticulocyte count – indicates on going red cell production, may be high if recovering from low production
• White cell count and platelets – if low too, suggests bone marrow failure but parvovirus can knock off all cell lines too.
• Coagulation – deranged coagulation with low platelets suggests disseminated intravascular coagulation (DIC), usually due to sepsis, but can also reflect haemophagocytosis syndrome (due to sepsis or rheumatological disease)
• Renal function – haemolytic uraemic syndrome (usually with diarrhoea and bloody stools, but not always)

Iron is found in red meat, pulses, green leafy vegetables, wholemeal bread, nuts, dried fruit, fortified breakfast cereals.