Adult T-cell leukaemia/lymphoma (ATLL) is a unique lymphoproliferative disorder [1–5] that develops only in individuals who are chronic carriers of the retrovirus, human T-cell lymphotropic virus 1 (HTLV-1) [6,7]. The interval between acquiring the virus and developing the lymphoma is usually 30–60 years with the life-time risk of developing ATLL being of the order of 2% for women and 6% for men. Since only a minority of HTLV-1 carriers develop ATLL it is clear that there must be co-factors that contribute to development of the condition; the nature of these remains unknown although Strongyloides stercoralis infection has been suspected. HTLV-1 can also cause polymyositis, arthritis, uveitis and HTLV-1-associated myelopathy (also known as tropical spastic paraparesis). In addition, it leads to immunosuppression, which is responsible for an increased incidence of infective dermatitis, Pneumocystis jirovecii pneumonia, S. stercoralis hyperinfection and virus-related tumours (e.g. carcinoma of the cervix, Kaposi’s sarcoma and hepatoma related to hepatitis viruses). Because of the distribution of HTLV-1, ATLL is distributed unevenly throughout the world. The best-recognized endemic areas are Japan (particularly the island of Kyushu) and the Caribbean but, in fact, there are likely to be more cases in South America and Central and West Africa, where carriers of the virus are even more numerous. Endemic cases have also been observed in Eastern Europe and in the Middle East. Cases are found in Europe and North America, among migrants from endemic areas. Familial ATLL has been documented in Japan, the United States and Europe; it is uncertain whether there is a genetic predisposition in these carriers of the retrovirus or whether instead it is the result of sharing the same environment.
About 20% of individuals who develop ATLL present with lymphoma without involvement of the peripheral blood or bone marrow. The other 80% have leukaemic manifestations. Four clinical forms defined by clinical and laboratory features have been described by Shimoyama et al.: acute, lymphoma, chronic and smouldering (Table 17.1) . Isolated primary cutaneous forms that raise problems of differential diagnosis with primary cutaneous T-cell lymphomas have been documented . There is usually lymphadenopathy (Figure 17.1) and there may be hepatomegaly, splenomegaly and skin infiltration (papules, nodules and plaques) (Figure 17.2). A minority of patients have pleural effusions, ascites or infiltration of lung, liver, gastrointestinal tract, leptomeninges or brain (Figure 17.3. Hypercalcaemia is a common clinical feature, either at presentation or during disease progression; it may be associated with lytic bone lesions and is the result of stimulation of osteoclasts by cytokines secreted by the neoplastic cells. Hypercalcaemia can lead to dehydration and renal impairment. The clinical course is usually acute but smouldering and chronic forms of the disease are well recognized.
Table 17.1Subclassification of adult T-cell leukaemia/lymphoma