HNY Policy and Pathway Repository - North Yorkshire

Macrocrocytosis with or without Anaemia (MCV >100).

None provided

Causes

Vitamin B12 and folate deficiencies are not the only causes of macrocytosis, other (non-megaloblastic) causes of macrocytosis include:

• Alcohol - may cause macrocytosis with neither anaemia not a change in liver fuction. Alcohol is the most frequent cause of a raised mean cell volume (MCV) in the absence of anaemis.
• Drugs - antimetabolites, such as hydroxycarbamide, methotrexate and azathioprine.
• Haematological abnormalities such as:
  • Myekidysplasia
  • Aplastic anaemia
  • Pure red cell aplasia
  • Plasma protein changes (for example myeloma)
  • Reticulocytosis
• Liver disease - chronic liver disease is associated with anaemia that is mildly macrocytic
• Pregnancy and the neonatal period
• Severe thyroid deficiency - anaemia caused by hypothyroidism is often macrocytic. However, MCV falls once thyroxine treatment is started.
• Smoking

Management

• Repeat FBC to ensure not spurious (e.g. delayed transport / overheating ect.)
• If MCV remains raised:
  • Alcohol history
  • Smoking history
  • Medication history
  • Blood film
  • VIT B12 and folate
  • Reticulocyte count / LDH
  • LFT
  • TFT
  • Consider myeloma screen (serum protein electrophoresis and urine BJP) if other causes excluded and there is anaemia. Not a first line investigation. Not indicated if no anaemia. 
• Underlying cause identified? Treat as appropriate and monitor for resolution.

Consider referral to Haematology if:

• No cause identified and MCV>105fL if any cytopenia or >100fL in the absence of cytopenia
• Primary haematological disorder is suspected e.g. dysplasia on blood film, paraprotein detected, evidence of haemolysis (e.g. raised BIL, reticulocytes, LDH).

Detailed guidance of investigation and management of B12 / folate deficiency available at: https://cks.nice.org.uk/topics/anaemia-b12-folate-deficiency/

See also BUKU medicine.

• Harrogate and District