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Disseminated superficial actinic porokeratosis (DSAP) is an uncommon autosomal dominant chronic disorder of keratinization, characterized by multiple superficial keratotic lesions surrounded by a slightly raised keratotic border. Thus far, although two loci for DSAP have been identified, and the genetic basis and pathogenesis of this disorder have not been elucidated.To determine the locus of DSAP and identify the candidate gene(s) of the disease.Genome-wide scan and linkage analysis were performed in a six-generation Chinese family with DSAP. The coding exons of the candidate genes were sequenced to analyse and detect the nucleotide variations.Linkage analysis showed that the maximum two-point lod score of 5·56 was obtained with the marker D12S79 at a recombination fractionθ of 0·00. Haplotype analysis defined the critical region for DSAP between D12S330 and D12S1612 on 12q24.1–24.2. By sequence analysis, we found a Val591Met mutation inSART3in all affected individuals of the family.SART3is a candidate gene for DSAP, and is possibly involved in the pathogenesis of DSAP. [ABSTRACT FROM AUTHOR]

Background Dyschromatosis symmetrica hereditaria (DSH) is an autosomal dominant pigmentary genodermatosis characterized by hyperpigmented and hypopigmented macules on the extremities, which has recently been mapped to an 11·6-cM interval on chromosome 1q11-21. So far, most cases of DSH have been reported in Japan and dermatologists around the world might think this disorder mainly occurs in Japan. In fact, there are 17 DSH families including 136 cases reported in China since 1980, but most of them are described in Chinese. Objectives To refine the previously mapped region that facilitates the identification of the DSH gene and to delineate the clinical and genetic features of Chinese DSH cases by a literature review of 136 cases reported in China. Methods We performed genotyping and linkage analysis using polymorphic microsatellite markers at 1q11-22 in two Chinese DSH families, and reviewed all of the DSH cases reported in China since 1980. Results A cumulative maximum two-point lod score of 3·68 was produced with marker DIS506 at a recombination frequency of θ = 0·00 in these two families. Haplotype analysis refined the DSH locus to a 9·4-cM interval flanked by D1S2343 and D1S2635. The genetic and clinical features of Chinese cases with DSH were summarized. In some Chinese cases, hyperpigmented and hypopigmented macules were scattered on the neck and chest, but among Japanese patients there were no similar skin lesions to be reported on these sites. Conclusions This study confirms linkage of DSH to a previously mapped region and refines the DSH gene to a 9·4-cM interval at 1q21-22. Likewise, the literature review indicates that DSH is not an uncommon disorder in China and the differences in the distribution of skin lesions could be related to race and environment. [ABSTRACT FROM AUTHOR]