High prevalence of the very rare Wilson disease gene mutation Leu708Pro in the Island of Gran Canaria (Canary islands, Spain):: A genetic and clinical study

The molecular basis of Wilson disease (WD), an autosomal recessive disorder, is the presence of mutations in the ATP7B gene, a copper transporting ATPase. Hospital records indicated a higher prevalence of WD (1 in 2,600) in some counties in the northeastern region of the island of Gran Canaria (Canary Islands, Spain) that was around 10-fold higher than that described for European populations (1 in 30,000). The ATP7B gene was analyzed for mutations in 24 affected subjects, revealing a high prevalence of the rare Leu708Pro mutation present in 12 homozygous and 7 heterozygous individuals. In these patients, who constitute one of the largest described cohorts of WD homozygotes, we found a variable clinical presentation of the disease, although the biochemical picture was homogenous and characteristic, thereby confirming that the Leu708Pro change is indeed a mutation associated with WD. Haplotype analysis of subjects homozygous for the Leu708Pro mutation showed a conserved shared region smaller than 1 centimorgan (cM), and the region of linkage disequilibrium between the Leu708Pro mutation and neighboring microsatellite markers extended approximately 4.6 cM. When comparing the amount of linkage disequilibrium versus genetic distance from the disease mutation, it was estimated that a common ancestral Leu708Pro chromosome may have been introduced in Gran Canaria over 56 generations ago, dating it back to pre-Hispanic times. The prevalence, and the tight geographical distribution of the Leu708Pro chromosome suggests that the Canary Islands can be considered a genetic isolate for linkage disequilibrium studies.