RESUMO
BACKGROUND: Previous research strongly suggest that malaria is an important factor in the pathogenesis of endemic Burkitt's lymphoma (eBL). Therefore, genetic factors such as sickle cell trait (SCT) and blood group-O that offer protection against severe malaria would be expected to reduce the risks of eBL. However, previous reports on the protective roles of SCT and blood group-O against the risks of eBL were inconclusive. Hence, the need for further studies on the protective roles of SCT and blood group-O separately, and also to investigate whether or not the combined anti-severe malaria protective roles of SCT and blood group-O have synergistic effects in reducing the risks of eBL. We therefore hypothesize that SCT and blood group-O are independently associated with reduced risks of eBL, and the co-inheritance of both factors (SCT and group-O) would provide greater protection against eBL. If our hypothesis is correct, children who inherited both SCT and blood group-O would have lower risks of eBL than their counterparts who inherited SCT or blood group-O separately. To the best of our knowledge, the possible synergistic relationship between SCT and blood group-O with regards to the risk of eBL has not been previously studied. PATIENTS AND METHODS: We conducted a retrospective logistic regression analysis of the frequencies of Hb phenotypes and ABO blood groups among patients with eBL in order to determine the separate and synergistic protective effects of SCT and blood group-O on the risk of eBL in Nigeria where eBL is among the most common malignant childhood cancers. RESULTS: The Odd Ratios (OR) for the risk of eBL were 0.52 for 'SCT irrespective of ABO blood group'; 0.49 for 'blood group-O irrespective of Hb phenotype'; and 0.23 for 'SCT with blood group-O'. DISCUSSION: These values suggest that both SCT and blood group-O are independently associated with modest reduction in the risk of eBL. However, when SCT with blood group-O was assessed for the risk factor for eBL, we obtained an Odds ratio of 0.23, which was significantly lower than the OR values for SCT (0.52) and blood group-O (0.49) separately. These figures suggest that coinheritance of SCT and blood group-O offers greater reduction in the risk of eBL than that provided by either SCT or blood group-O separately. The greater protection against eBL provided by the coinheritance of SCT and blood group-O is interpreted to be the resultant synergistic effect of the combined anti-malarial attributes of SCT and blood group-O. CONCLUSION: These findings suggest that the combined anti-malarial protective roles of SCT and blood group-O have synergistic effects in reducing the risks of eBL. This study has provided further evidence on the association between malaria-protective genetic polymorphisms and eBL, which is consistent with the aetiologic role of malaria in the pathogenesis of the tumour. Hence, the need for malaria endemic countries to intensify malaria control programs in order to curtail the incidence of eBL.