Mutations in the iduronate-2-sulfatase gene in five Norwegians with Hunter syndrome.

We have identified the mutations in the iduronate-2-sulfatase (IDS) gene of five unrelated Norwegians with Hunter syndrome by reverse transcription-polymerase chain reaction (RT-PCR) analysis of IDS mRNA followed by single strand conformation polymorphism (SSCP) analysis and cDNA sequencing. One patient had a 5-bp deletion, located at the intron 5/exon 6 junction, that created a new alternative splice site. This expanded the deletion to 9 bp in mRNA, an in-frame deletion of the first 3 codons of exon 6 of the IDS gene. In two patients point mutations were identified, the S333L mutation, which has been reported previously, and A346D (a C-->A transversion at nucleotide 1161/exon 8), which is novel. Two patients had large 3' mRNA rearrangements. The A346D mutation was associated with the mild phenotype, all others with the severe form.