Lymphocytosis is a common finding.

Transient increases in the lymphocyte count (lymphocytosis) are usually due to acute infections e.g. viral infections, pertussis. If there is persistent lymphocytosis, consider these causes:

  • Auto-immune conditions, e.g. rheumatoid arthritis
  • Smoking
  • Post splenectomy
  • Monoclonal B-cell lymphocytosis (a clonal lymphocytosis similar to CLL but with clonal lymphocytes less than 5 x 109/L and without other features of CLL)
  • Chronic Lymphocytic Leukaemia (CLL)
  • Alternative low grade lymphoproliferative disorders (e.g. Follicular Lymphoma)


Signs and Symptoms

Look for:

  • Clinical signs of infection or inflammation
  • Lymphadenopathy or hepatosplenomegaly


  • If well or mild symptoms, recheck white count in 1 to 2 months. Reactive lymphocytosis generally resolves within 2 months
  • A stable increased lymphocyte count in an otherwise well person is unlikely to require treatment and does not always need further assessment
  • Asymptomatic low grade lymphoproliferative disorders (including CLL) do not benefit from earlier treatment


Referral Criteria

Request a haematology assessment if lymphocytosis is associated with:

  • rapidly rising lymphocyte count (i.e. more than 20 x 109/L and doubling time of less than 6 months) or blast cells present
  • lymphadenopathy or hepatosplenomegaly
  • anaemia, neutropenia, or thrombocytopenia

Referral Instructions

e-Referral Service Selection

  • Specialty: Haematology
  • Clinic Type: Not otherwise specified
  • Service: DRSS-Northern-Haematology-NEW Devon CCG

Referral Forms

DRSS Referral Form

Supporting Information

Pathway Group

This guideline has been signed off by NEW Devon CCG.

Publication date: June 2016


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