In Western countries, chronic lymphocytic leukaemia (CLL) is by far the most common lymphoid malignancy [1–3]. It is a disease predominantly of the middle aged and elderly with the incidence being considerably higher in men than in women. In some instances, a familial predisposition to develop CLL can be demonstrated  and family members may have monoclonal B-cell lymphocytosis (MBL) with a higher frequency than the general population . Diagnosis requires the presence of significant lymphocytosis, often arbitrarily defined as a lymphocyte count exceeding 5 × 109/l of circulating clonal B cells with a CLL phenotype. There is often a long asymptomatic phase in CLL so that incidental diagnosis is common and many patients subsequently die with the disease rather than of the disease.
Small lymphocytic lymphoma is a lymphoma in which the neoplastic cells have the same cytological and immunophenotypic features as those of CLL but without there being significant lymphocytosis at diagnosis. In some patients with small lymphocytic lymphoma, a leukaemic phase subsequently occurs.
One form of MBL is defined by the presence of <5 × 109/l circulating clonal B cells with a CLL phenotype in the absence of organ involvement. Two subgroups of MBL are recognized: low count (<0.5 × 109/l) MBL and high count (>0.5 × 109/l. Another form of MBL is that designated MBL-non CLL type. These patients have identical manifestations to those with MBL-CLL type but the phenotype is not that of CLL. In such a situation, a spill over of a B-cell lymphoma should always be excluded with the appropriate investigations .
In patients in whom the diagnosis of CLL is incidental there may be no symptoms and no abnormal physical findings. In other patients with more advanced disease, presentation may be with lymphadenopathy, with or without splenomegaly or hepatomegaly, or with infection, bruising or symptoms of anaemia (Figures 3.1 and 3.2). Infections that are particularly prevalent among these patients are herpes zoster (Figure 3.3) and pneumococcal pneumonia. Autoimmune complications, specifically autoimmune haemolytic anaemia, autoimmune thrombocytopenic purpura and pure red cell aplasia, may be present at diagnosis and are common during the course of the disease. Small lymphocytic lymphoma usually presents with lymphadenopathy, with or without splenomegaly or hepatomegaly.
Clinical photograph showing cervical lymphadenopathy in a patient with chronic lymphocytic leukaemia (CLL).
Clinical photograph showing skin infiltration in a patient with CLL.
Clinical photograph showing herpes zoster in a patient with CLL.