Background: Familial nonmedullary thyroid cancer (FNMTC) is associated with earlier onset and more aggressive behavior than its sporadic counterpart. Although candidate chromosomal loci have been proposed for isolated families with variants of FNMTC, the etiology of most cases is unknown. We aimed to identify loci linked to FNMTC susceptibility using single-nucleotide polymorphism (SNP) array-based linkage analysis in a broad sampling of affected families. Methods: We enrolled and pedigreed 38 FNMTC families. Genomic DNA was extracted from the peripheral blood of 110 relatives, and hybridized to Affymetrix SNP arrays. We performed genotyping and linkage analysis, calculating exponential logarithm-of-the-odds (LOD) scores to identify chromosomal loci with a significant likelihood of linkage. Results: Forty-nine affected and 61 unaffected members of FNMTC families were genotyped. In pooled linkage analysis of all families, 2 distinct loci with significant linkage were detected at 6q22 and 1q21 (LOD = 3.3 and 3.04, respectively). Conclusion: We have identified 2 loci on chromosomes 1 and 6 that demonstrate linkage in a broad sampling of FNMTC families. Our findings suggest the presence of germline mutations in heretofore-undiscovered genes at these loci, which may potentially lead to accurate genetic tests. Future studies will consist of technical validation and subset analyses of higher-risk pedigrees.
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