Confirmation of an association between the TNF(-308) promoter polymorphism and stroke risk in children with sickle cell anemia.

BACKGROUND AND PURPOSE: The etiology of stroke in children with sickle cell anemia (SCA) is complex and poorly understood. Growing evidence suggests that genetic factors beyond the sickle cell mutation influence stroke risk in SCA. We previously reported risk associations with polymorphisms in several proinflammatory genes in SCA children with ischemic stroke. The aim of this replication study was to confirm our previous findings of associations between the TNF(-308) G/A, IL4R 503 S/P, and ADRB2 27 Q/E polymorphisms and large vessel stroke risk.

METHODS: Using previously collected MRA data, we assessed an independent population of SCA children from the multicenter Stroke Prevention Trial in Sickle Cell Anemia (STOP) for the presence or absence of large vessel stenosis. Samples were genotyped for 104 polymorphisms among 65 candidate vascular disease genes. Genotypic associations with risk of large vessel stroke were screened using univariable analysis and compared with results from our original study. Joint analysis of the 2 study populations combined was performed using multivariable logistic regression.

RESULTS: A total of 96 children (49 MRA-positive, 47 MRA-negative) were included in this study. Of the SNP associations previously identified in the original study, the TNF(-308) G/A association with large vessel stroke remained significant and the IL4R 503 S/P variant approached significance in the joint analysis of the combined study populations. Consistent with our original findings, the TNF(-308) GG genotype was associated with a >3-fold increased risk of large vessel disease (OR=3.27; 95% CI=1.6, 6.9; P=0.006). Unadjusted analyses also revealed a previously unidentified association between the LTC4S(-444) A/C variant and large vessel stroke risk.

CONCLUSIONS: Similar findings in 2 independent study populations strongly suggest that the TNF(-308) G/A promoter polymorphism is a clinically important risk factor for large vessel stroke in children with SCA. The previously observed association with the IL4R 503 S/P variant and the novel association with the LTC4S(-444) A/C variant suggest that these loci may also contribute to large vessel stroke risk in children with SCA.