Chronic Lymphocytic Leukaemia in Tropical Africa: A Review

Abstract

Chronic lymphocytic leukaemia (CLL) has a male:female (M:F) ratio 1:1 in tropical Africa. Below the age of 45 years, the M:F is 1:2, while above 45 years; it is 2:1 CLL in younger adults is associated with low socio-economic status (SES) and rural habitation. Clinical and haematological features are the same as in other continents, except that many patients have gross splenomegaly and two populations of lymphocytes in the peripheral blood on light microscopy: it is postulated that with the altered immunity of CLL, recurrent malaria causes a secondary but benign lymphoid hyperplasia.

It is hypothesised that the probability of B-cell mutation is increased in an enlarged pool of B-cells resulting from recurrent malaria and other infections. The greatest enhancement occurs in subjects of low SES, who are more exposed to infections, and in grandemultiparae, whose cell-mediated immunity has been depressed repeatedly during pregnancies. A second event could follow transmission of an unidentified virus: transmission is more likely with overcrowding and proliferation more rapid with depression of immunity by malaria and pregnancy. HTLV-1 is associated with CLL, but does not appear to contribute significantly to the peculiar epidemiology of CLL in Africa.

Key Words:

• Chronic lymphocytic leukaemia
• lymphocytes
• Epidemiology
• Africa
• Malaria