Mendelian Genes and Risk of Intracerebral Hemorrhage and Small-Vessel Ischemic Stroke in Sporadic Cases

BACKGROUND AND PURPOSE: Mendelian strokes are rare genetic disorders characterized by early-onset small-vessel stroke. Although extensively studied among families with syndromic features, whether these genes affect risk among sporadic cases is unknown. METHODS: We sequenced 8 genes responsible for Mendelian stroke in a case-control study of sporadic stroke cases (≤70 years). Participants included 1251 primary stroke cases of small-vessel pathology (637 intracerebral hemorrhage and 614 small-vessel ischemic stroke cases) and 1716 controls from the INTERSTROKE study (Study of the Importance of Conventional and Emerging Risk Factors of Stroke in Different Regions and Ethnic Groups of the World). RESULTS: Overall, the prevalence of canonical disease-causing mutations was 0.56% in cases and 0.23% in controls (odds ratio=1.89; 95% confidence interval, 0.54-7.57; P=0.33). CADASIL (Cerebral Autosomal Dominant Arteriopathies with Subcortical Infarcts and Leukoencephalopathies) mutations were more frequent among cases (0.48%) than controls (0.23%) but were not significantly associated with stroke risk (odds ratio=2.03; 95% confidence interval, 0.58-8.02; P=0.27). Next, we included all rare nonsynonymous mutations to investigate whether other types of mutations may contribute to stroke risk. Overall, 13.5% of cases and 14.2% of controls were carriers of at least one rare nonsynonymous mutation among the 8 Mendelian stroke genes. Mutation carriers were not at elevated risk of stroke (odds ratio=0.93; 95% confidence interval, 0.75-1.16; P=0.55). CONCLUSIONS: In the absence of syndromic features and family history of stroke, screening for Mendelian mutations among small-vessel stroke patients is unlikely to have high diagnostic utility.