Isolated elevated sweat chloride concentrations in the presence of the rare mutation S1455X: An extremely mild form ofCFTR dysfunction

Mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) have been shown to cause typical cystic fibrosis (CF) and several milder phenotypes. We report on two asymptomatic sisters who had isolated increased sweat chloride concentrations, and in whom systematic scanning of the whole coding region of the CFTR gene revealed the F508del/S1455X genotype.

The necessity of complete CFTR mutational analysis of an infertile couple before in vitro fertilization

OBJECTIVE

To determine the genotype of a triplet resulted from an IVF procedure, with discordant cystic fibrosis (CF) phenotype.

DESIGN

Molecular diagnosis of CF.

SETTING

Affected triplet followed at the CF Clinic Center of Children's Hospital Los Angeles was referred to Molecular Genetics Laboratory at Georgetown University Medical Center for comprehensive DNA analysis of the cystic fibrosis transmembrane regulator (CFTR) gene.

PATIENT(S)

Three affected children and the healthy parents with negative family history of CF.

MAIN OUTCOME MEASURE(S)

Temporal temperature gradient gel electrophoresis and direct DNA sequencing were used to detect and to identify the mutations.

RESULT(S)

The child with classic CF had DeltaF508 and R553X mutations. Two children with mild CF symptoms had DeltaF508 and R117C. The father carried two mutations, R553X and R117C. The mother is a carrier for DeltaF508.

CONCLUSION(S)

Mutational analysis of the CFTR gene should always be recommended to the infertile couples seeking for IVF. The CFTR mutation screening would be essential if the man has congenital bilateral absence of vas deferens (CBAVD) despite the negative family history of CF. Option of complete CFTR gene analysis at a cost of about 1,500-2,000 dollars should be made available if one mutation is found in the male partner with congenital bilateral absence of vas deferens.

Newborn screening for cystic fibrosis

Early diagnosis of cystic fibrosis (CF) provides an opportunity to improve disease control and prevent early complications. Of patients with CF in the United States, 10% are identified early through newborn screening (including infants born in Colorado, Massachusetts, New Jersey, New York, Wisconsin, Wyoming, and parts of California, Connecticut, Pennsylvania, and Montana). Successful screening programs in these states have stimulated other states to consider adding CF screening to their newborn programs. Additionally, new technology permits expanded screening for numerous genetic conditions. Genetic screening, such as that used most frequently for CF, creates new challenges for the clinician, including atypical disease presentations and carrier detection. In this review, we examine the many advances in CF newborn screening and early care that were reported during the last few years.

The I148T CFTR allele occurs on multiple haplotypes: a complex allele is associated with cystic fibrosis

PURPOSE

To determine whether intragenic changes modulate the cystic fibrosis (CF) phenotype in individuals who are positive for the I148T allele.

METHODS

The genes from individuals who carried at least one copy of the I148T allele were analyzed for additional changes that may be acting as genetic modifiers.

RESULTS

Seven of eight individuals with a known or suspected diagnosis of CF who carried I148T in combination with a severe CF mutation also carried 3199del6. Eight apparently healthy adult individuals who were compound heterozygous for I148T and a severe CF mutation or homozygous for I148T did not carry the deletion ( = 0.0014). The I148T allele occurs on at least three haplotypes: an IVS-8 9T background, a 7T background, or a 9T + 3199del6 background. The 3199del6 allele was not identified in 386 non-CF chromosomes.

CONCLUSIONS

It is concluded that I148T occurs on at least three haplotypes and the complex allele I148T + 9T + 3199del6 is associated with a classic CF phenotype.