Here we describe a previously unreported IDUA splice site mutation (NG_008103.1:g.21632G>C; NM_000203.3:c.1727+3G>C) causing a Hurler phenotype in a patient heterozygous for the common p.Q70X (NG_008103.1:g.5862C>T) mutation.
The premature stop codons Q70X and W402X are two of the most common alpha-l-iduronidase gene (IDUA) mutations accounting for up to 70% of MPS I disease alleles in some populations.
We found that a Hurler syndrome fibroblast cell line heterozygous for the IDUA stop mutations Q70X and W402X showed a significant increase in alpha-L-iduronidase activity when cultured in the presence of gentamicin, resulting in the restoration of 2.8% of normal alpha-L-iduronidase activity.
Previous studies in Caucasian populations showed that (1) homozygosity or compound heterozygosity for the W402X and Q70X mutations are the common causes of MPS-I with a severe form (Hurler syndrome), and (2) the presence of R89Q may lead to a milder phenotype.