Dyskeratosis congenita (DC) is a rare inherited disorder characterised by the 
early onset of reticulate skin pigmentation, nail dystrophy, and mucosal 
leucoplakia. In over 80% of cases bone marrow failure develops and this is the 
main cause of early mortality. The DC1 gene responsible for the X linked form 
(MIM 305000) of dyskeratosis congenita has been mapped to Xq28. In order to 
narrow the candidate gene region, genetic linkage analysis was performed in 
eight X linked pedigrees using a set of markers spanning Xq28. A maximum lod 
score of 5.31 with no recombinations was achieved with marker DXS1073. Two 
recombination events were identified; one of these uses X chromosome 
inactivation pattern analysis to determine carrier status and haplotype analysis 
to fine map the recombination breakpoint. The fine mapping of these 
recombination events has enabled the candidate gene region for X linked 
dyskeratosis congenita to be defined as the 1.4 Mb interval between Xq3274 and 
DXS1108.