Mucopolysaccharidosis type I: molecular characteristics of two novel alpha-L-iduronidase mutations in Tunisian patients

BACKGROUND Mucopolysaccharidosis type I (MPS I) is an autosomal storage disease resulting from defective activity of the enzyme α-L-iduronidase (IDUA). This glycosidase is involved in the degradation of heparan sulfate and dermatan sulfate. MPS I has severe and milder phenotypic subtypes. AIM OF STUDY This study was carried out on six newly collected MPS I patients recruited from many regions of Tunisia. PATIENTS AND METHODS Mutational analysis of the IDUA gene in unrelated MPS I families was performed by sequencing the exons and intron-exon junctions of IDUA gene. RESULTS Two novel IDUA mutations, p.L530fs (1587_1588 insGC) in exon 11 and p.F177S in exon 5 and two previously reported mutations p.P533R and p.Y581X were detected. The patient in family 1 who has the Hurler phenotype was homozygous for the previously described nonsense mutation p.Y581X.The patient in family 2 who also has the Hurler phenotype was homozygous for the novel missense mutation p.F177S. The three patients in families 3, 5 and 6 were homozygous for the p.P533R mutation. The patient in family 4 was homozygous for the novel small insertion 1587_1588 insGC. In addition, eighteen known and one unknown IDUA polymorphisms were identified. CONCLUSION The identification of these mutations should facilitate prenatal diagnosis and counseling for MPS I in Tunisia.