Hunter disease or mucopolysaccharidosis type II is an X-linked disease caused by 
the deficiency of the lysosomal enzyme iduronate-2-sulfatase (IDS). The IDS gene 
(24 kb) contains nine exons and has been completely sequenced. A pseudogene 
(IDS-2 locus) distal to the functional IDS gene has recently been identified. 
This work reports the characterization of IDS gene alterations in two severely 
affected patients. Patient 1 has a partial deletion that removes exons I to VI 
and extends about 200 kb upstream of the IDS gene. Patient 2 has an internal 
deletion of exons IV, V, VI, and VII, which results from an IDS gene-pseudogene 
exchange between highly homologous regions. In the rearranged gene, the junction 
intron contains pseudogene intron 3- and intron 7-related sequences. An 
interchromosomal recombination is probably the cause of this rearranged X 
chromosome.