Monocytosis (Guidelines)

TAM (Treatments and Medicines) NHS Highland
NHS Highland

Audience

The normal reference range is 0.2 to 0.8 × 109/L and monocytosis is frequently transient.

Causes

  • Infections eg. tuberculosis, brucella, malaria, syphilis, endocarditis
  • Autoimmune and inflammatory diseases
  • Stress response g. post myocardial infarction
  • Sarcoidosis
  • Hyposplenism
  • Chronic myelomonocytic leukaemia
  • Malignancy

History and examination

Look for signs of infection including atypical infections. Ask about a travel history. Examine for splenomegaly and hepatomegaly. Ask about weight loss, rashes and night sweats. Look at older blood counts.

Suggested investigations

  • Blood film
  • Inflammatory markers
  • Renal and liver function
  • Calcium

Management

If the monocytosis is persistent this may represent chronic myelomonocytic leukaemia. This is a chronic and generally incurable disorder. Some cases behave indolently and others can be more aggressive.

Suggest referral if:

  • Persistent monocyte count over 5 × 109/L
  • Monocyte count over 2 × 109/L with other significant cytopenia(s) or concerning symptoms or abnormal features on blood film

If the monocyte count is between 1.2 and 5 × 109/L with no other cytopenia and no constitutional symptoms or symptomatic splenomegaly then suggest discuss via Clinical Dialogue and then monitor every 6 to 12 months.

Editorial Information

Last reviewed: 29/01/2024

Next review date: 31/01/2027

Author(s): Haematology Department .

Version: 2

Approved By: APPROVED TAM Subgroup of the ADTC

Reviewer name(s): Dr P Forsyth, Consultant Haematologist .

Document Id: TAM616