Chronic lymphocytic leukaemia (CLL) is a B-cell clonal lymphoproliferative disease in which lymphocytes accumulate in the blood, bone marrow, lymph nodes and spleen (absolute clonal B lymphocyte count >5.0 × 109/L). A disease of older patients (peak age 72 years), it is the most common leukaemia in Western countries (over 70 new cases per million population per year in the UK; male : female ratio 2 : 1) but is rare in Asia. Small cell lymphocytic lymphoma is an identical disease without lymphocytosis in the blood (see Chapter 33).
Aetiology and pathophysiology
The cause is unknown. The most common chromosome changes are trisomy 12, a 13q deletion and deletions of 11q including the ataxia telangiectasia (ATM) gene. Oncogene mutations e.g. of NOTCH1 or deletions occur, which may prevent cells from undergoing apoptosis. The 13q deletion is thought to eliminate expression of several micro-RNAs (see Chapter 20). Mutations or deletions of the P53 gene (chromosome 17) concerned in DNA repair may be present. They have adverse prognostic significance. Mutation of a gene involved in splicing messenger RNA occurs in 15% of cases. This is identical to the mutation found in some cases of myelodysplasia.
Monoclonal B lymphocytosis (MBL) is similar to Stage A CLL but the absolute clonal B lymphocyte count in the blood is <5.0 × 109/L. There are no other clinical or laboratory abnormalities. CLL is thought to start as MBL but most cases of MBL do not progress to CLL.
Clinical features
Stage depends on the extent of lymphadenopathy, if present, spleen size and blood count findings (Fig. 29.1).
- Most cases (Stage A) are symptomless and diagnosed on routine blood test. Lymphadenopathy is absent.
- Presenting features in Stage B or C cases include lymphadenopathy (typically symmetrical, painless and discrete), night sweats, loss of weight, symptoms due to bone marrow failure.
- Spleen is often moderately enlarged in Stages B or C.
- Hypogammaglobulinaemia and reduced cell-mediated immunity predispose to bacterial and viral infection e.g. shingles.
- Autoimmune haemolytic anaemia occurs in 15–25% of cases.
Laboratory findings
- Increased peripheral blood lymphocytes (Fig. 29.2; usually 5–30 × 109
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