Abstract: Objective To map the locus of the gene CYLD1 for multiple familial trichoepithelioma (MFT), and identify the mutation of this gene in a large Chinese Han family with MFT. Methods The local genome scan was performed using 18 microsatellite markers spanning 9p21 and 16q12-q13 in this MFT family. Linkage software was used for two-point linkage analysis. All 17 coding exons of the CYLD1 gene and the adjacent splice sites were amplified using PCR. Mutation scanning was carried out by DNA sequencing. Results ① Two-point linkage analysis revealed a LOD score of 3.31 under the assumption of an autosomal dominant inheritance with disease-allele frequency of 0.00001 and penetrance of 99.9%. ② A four-basepair deletion of exon 18 in the CYLD1 gene was detected, designated c.2355-2358delCAGA. Conclusions Multiple familial trichoepithelioma is a genetically heterogeneous disorder. The gene CYLD1 for this MFT family localizes to 16q12-q13, not 9p21.

Key words: Trichoepithelioma, Genes, Genetic heterogeneity