Hunter disease in the Spanish population: molecular analysis in 31 families.

Mucopolysaccharidosis type II (Hunter disease) is an X-linked disorder due to deficiency of the lysosomal enzyme iduronate 2-sulphatase. Here we report an update of molecular studies in 31 Spanish families with Hunter disease. We found a total of 22 novel small mutations (7 reported previously by our group), and 4 large deletions or rearrangements. Particularly relevant are two mutations, one showing an alternatively spliced product although the normal splice site is conserved; the other mutation results in an amino acid change that most likely modifies regulation of expression of the IDS gene. Except for large gene alterations and for the G374sp mutation already described, we could not establish a clear phenotype-genotype correlation. Mutation G374sp is the point mutation most frequent in our population (10%) and is always associated with mild phenotype. Our molecular analyses carried out in a relatively large series of patients with Hunter disease contribute to the identification of new mutations and reinforce the conclusions drawn in other populations about the genotype-phenotype correlation and the gene distribution of mutations.