Copyright ©ERS Journals Ltd 2001 Intron-8 polythymidine sequence in Australasian individuals with CF mutations R117H and R117C1 Dept of Respiratory Medicine, Royal Children's Hospital, Melbourne, Australia, 2 Dept of Chemical Pathology, Women's and Children's Hospital, North Adelaide, Australia, 3 Royal Alexandra Hospital for Children, Sydney, Australia, 4 Princess Margaret Hospital for Children, Perth, Australia, 5 Starship Children's Hospital, Auckland, New Zealand CORRESPONDENCE: R.J.H. Massie, Dept of Respiratory Medicine, Royal Children's Hospital, Melbourne, 3052, Australia. Fax: 61 393491289 Keywords: cystic fibrosis, genotype, phenotype, R117H
Received: June 26, 2000
Compound heterozygotes for a severe cystic fibrosis transmembrane conductance regulator (CFTR) mutation and the R117H or R117C mutation (R117H/C) have clinical presentations that vary from classic cystic fibrosis (CF) to an incidental genetic finding.
The aim of this study was to assess the influence of the intron-8 polythymidine sequence (IVS8) on the relationship between genotype and phenotype of individuals with R117H/C.
All individuals with R117H/C known to CF clinics in Australia and New Zealand were retrospectively studied by collecting information on genotype, age, pancreatic status, sweat electrolytes, sputum microbiology and pulmonary function.
Forty-one individuals (39 with R117H and two with R117C), 16 on an IVS8-5T background and 25 on an IVS8-7T background were identified. Twelve individuals presented clinically, four were siblings of known R117H/C compound heterozygotes and 25 were detected by newborn screening. Eleven of 14 of the IVS8-5T group (78%) with sweat chloride results available had sweat Cl>60 mmol·L1 compared to 5 (20%) of the R117H/7T group (Chi-squared=10.4, p=0.001). Two were pancreatic insufficient, both IVS8-5T. Two IVS8-5T individuals have recently died (aged 43 and 19) and of the 14 surviving IVS8-5T group, 11 (79%) are symptomatic compared to eight (32%) of the IVS8-7T individuals (Chi-squared=6.1, p=0.01).
In conclusion, most individuals with R117H/C on a IVS8-5T background have an elevated sweat chloride and clinical cystic fibrosis, which in some cases is severe. Most individuals with R117H/C on an IVS8-7T background do not have clinical cystic fibrosis but should be followed for the development of clinical disease.
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