Influence of life-style on the pattern of leukaemia and lymphoma subtypes among Nigerians

Descriptive epidemiology of de novo acute leukaemia in the Sultanate of Oman

A hospital-based epidemiological study of de novo acute leukaemia was carried out in the Sultanate of Oman, a sparsely populated Arabian Gulf country which has undergone rapid and dramatic socio-economic changes recently. A total of 65/99 Omanis (66%) were diagnosed as acute lymphoblastic leukaemia (ALL) and 34/99 (34%) as acute myeloid leukaemia (AML). Trends and peak values in age-specific incidence rates for ALL are generally in line with those of Western countries. The proportion of T-ALL cases is however higher than that in Caucasian populations but lower than in many non-white populations. AML frequency particularly in childhood is similar to that observed in many African countries.

Unusual distribution of childhood cancer in Namibia

A survey of childhood cancer was undertaken in Namibia from 1983 to 1988 to record all tumors in children less than 15 years of age. The national incidence of childhood cancer in the republic of Namibia was 55.5 per million children. The overall incidence rate was 73.3 per million in urban and densely populated areas, and 44.4 per million in the rural areas. This difference was not statistically significant. The relatively high 75 per million overall incidence of tumors amongst the white population group was probably due to the generally higher socioeconomic status and concomitant good medical care of this ethnic group during the study period. The significantly higher overall incidence of tumors (109 per million) recorded in the Rehoboth ethnic group, however, could not be accounted for by socioeconomic status or better health care facilities and remains unexplained. The cause of the increased incidence of central nervous system tumors in the Herero (26 per million) and osteosarcomas in the Kavango (11 per million) ethnic groups is also not clear and warrants further research. The apparent geographical cluster of tumors in northern and central Namibia was caused by the irregular distribution of the population.

Leukocyte migration inhibition studies and neutrophil cell function during aging in Nigerians

In this study, in vitro cell-mediated immune response was analysed in 150 healthy Nigerians between 6 and 95 years old by the leukocyte migration inhibitory factor (L-MIF) test. Lymphocytes were activated with the mitogen concanavalin A and candida, measles virus and mycobacterial antigens. Nonspecific cellular immune capacity was studied by the Nitroblue tetrazolium (NBT) test. Numerical estimates of leukocytes and lymphocyte subpopulations were done. Mean L-MIF activity obtained with the four lymphocyte activators decreased with rising age indicating a progressive decline in cellular immune function with age. There was no significant age-related change in formazan positivity rate for both unstimulated and stimulated NBT tests. No age-related change in number was observed for any of the leucocyte and lymphocyte subpopulations. These results show that cell-mediaging response in Nigerians immunity declines, but phagocyte function is unchanged during aging. Lymphocyte depletion or numerical alteration in resting T cell subsets could not be demonstrated to be responsible for depressed cell-mediated immunity in aging Nigerians.

Epidemiology of acute leukaemia in the Cape Province of South Africa

Of 535 consecutive cases of acute leukaemia diagnosed in the Cape Province between 1978 and 1985, demographic data are incomplete in 75 black patients and they have had to be excluded from the spatial analysis. Of the remaining 460 cases, 223 (48.5%) occurred in white patients and 237 (51.5%) in those of mixed ancestry, classified as coloureds according to the Population Registration Act No. 30 of 1950. The average incidence was 2.12, 1.37 and 0.58/100,000 for whites, coloureds and blacks respectively. There was no temporal trend in the incidence of acute leukaemia between the three race groups. The median age for whites was 30 years and for the coloureds was 15 years, which is comparable to the 16 years for the black patients. The two-peak age distribution for leukaemia was seen in the white group, but was absent in the other two groups. This is accounted for by a different distribution in non-lymphoblastic as opposed to lymphoblastic subtypes. Furthermore, there was a disproportionately high frequency of acute progranulocytic leukaemia in the black patients, whereas the white and coloured groups were similar. There was a single, clearly defined macro-scale cluster restricted to white patients in Statistical Region 17 (SR-17). This exploratory study provides the first epidemiologic data for acute leukaemia in the Cape Province. It needs to be extended in order to verify these observations under more controlled circumstances and to seek evidence for some environmental factors that may account for the geographical cluster.

Lymphomas in University College Hospital, Ibadan, Nigeria

The authors reviewed 508 cases of lymphoma seen during a 16-year period in University College Hospital, Ibadan, Nigeria. Hodgkin's disease was diagnosed in 95 (18.6%) patients, of which 45% had mixed cellularity type; 19%, lymphocyte predominance; 18%, nodular sclerosis; and 18%, lymphocyte depletion. The age distribution showed a single mode in the 11 to 25-year-old group. Male preponderance was more marked in children who made up 32% of the Hodgkin's disease patients. Non-Hodgkin's lymphoma occurred in 413 cases, of which 296 (71.7%) were high-grade malignancies. Burkitt's tumor occurred in 211 (41.5%) patients, 95% of whom were children, and showed a male to female ratio of 1.7:1. Compared with previous findings in this hospital, Hodgkin's disease showed increased proportions of the lymphocyte predominant and nodular sclerosing types. However, the characteristics of Burkitt's lymphoma did not change appreciably in the last three decades.

Possible aetiological factors in leukaemias in Africa

The hypothesis that the true incidence of c-ALL is relatively uniform throughout the world is not supported by experience in tropical Africa, where ALL is uncommon under five years of age. A high rate of spontaneous somatic mutation in pre-B cells may initiate the development of c-ALL, but its progress could be determined by (i) a leukaemogenic agent causing a second genetic event, (ii) the effects of intense antigenic barrage, either stimulating or suppressing pre-B-cell mitosis, or (iii) genetic determinants. Epidemiological patterns in populations of low, intermediate and high socio-economic status may be classified I-III with increasing incidence of diagnosed T-ALL in children over five years and c-ALL in younger children, and subclassified A and B with decreasing incidence of BL. There may be two forms of AML, one similar to that seen in industrialized countries, the other occurring at high prevalence in African children of low socio-economic status, often presenting with chloroma, and perhaps associated with immune suppression secondary to malnutrition, malaria and other intercurrent infections. Uncontrolled exposure to petroleum and other chemicals, and the use of alkylating agents in treatment of neoplasms in young patients could emerge as important causes of ANLL in Africa. There are two varieties of CLL also, one similar to that seen in the western world, the other prevalent in adults below 45 years of age, especially women: transmission of a leukaemogenic agent is postulated, to which women are more susceptible due to immunosuppression during normal pregnancy. The human population and some subhuman primates of subSaharan Africa are the largest reservoir of HTLV-1, which shows association with B-CLL over 50 years of age and ATL.

Antibodies to HTLV-I in Nigerian blood-donors, their relatives and patients with leukaemias, lymphomas and other diseases

Antibodies to HTLV-I have been detected in sera from 15 (2.0%) of 736 adult blood-donors in Nigeria, in 4 (20.0%) of 20 patients with chronic lymphatic leukaemia, 3 (10.0%) of 30 with non-Hodgkin's lymphoma, one of 12 with Burkitt's lymphoma and one of 7 with acute lymphoblastic leukaemia. The frequency of positivity was higher (3.6%) in the blood-donors from the guinea and wooded savanna of northern Nigeria than in those from the rain-forest and mangrove swamps of southern Nigeria (1.8% in Lagos and 0.7% in Calabar). Two of the 3 seropositive patients with lymphoma had clinical presentation and courses similar to those of Japanese and Caribbean patients with adult T-cell leukaemia/lymphoma.

T-cell acute lymphoblastic leukemia in Israel: clinical and laboratory features

T-cell acute lymphoblastic leukemia (ALL) comprises a third of the cases of childhood ALL in Israel. This high proportion of T-ALL is most probably due to a deficiency in pre-B/common ALL. The T-ALL patients had significantly worse 4-yr survival compared to standard risk or non-T high risk patients. In view of these special epidemiologic and clinical features a study of the immunophenotype of all consecutive cases of T-ALL and T-non Hodgkin's lymphoma (NHL) observed in our medical center was performed. Twenty-eight ALL and 3 NHL patients were studied and their cells characterized using a panel of monoclonal antibodies, TdT reactivity and E-rosette formation. Assays of the activities of adenosine deaminase (ADA) and purine nucleoside phosphorylase (NP) were also performed. Based on the surface antigen expression, the tumor cells could be classified into one of the three known developmental stages of T cells. It was found that the immunophenotype of the T-ALL cases in Israel was similar to that observed in other countries. Considerable heterogeneity of surface antigen expression was found and in a number of cases the phenotype analysis was not easily reconciled with models of T-cell ontogeny. The activities of ADA and NP were correlated with the developmental stage, as defined by the surface antigenic expression. Contrary to observations on normal T-cells, where ADA activity decreases and NP activity increases as T-cells mature and differentiate, this was not found in the malignant T cells. These findings as well as the existence of atypical immunophenotypes suggest that the leukemic T cell has an abnormal gene expression.

A bibliography of the leukaemias in Africa, 1904-1985

A bibliography of leukaemias in Africa is presented from 1904 to 1985. The literature is listed chronologically and is classified geographically (north, south, east and west Africa) and by leukaemia type. The epidemiology of leukaemias in Africa is discussed briefly, especially as to the rarity of acute lymphoblastic leukaemia under the age of four years, the frequency of chloroma, the young age of presentation of chronic granulocytic leukaemia, the frequency of chronic lymphatic leukaemia in adults, especially women, under 45 years in tropical Africa, and the frequency of infection by the human T-cell leukaemia-lymphoma (or lymphotropic) virus type I and of adult T-cell leukaemia-lymphoma.