Genetic testing for cystic fibrosis in adult patients
Background: Cystic fibrosis (CF) is an autosomal recessive disease caused by mutations in gene encoding cystic fibrosis transmembrane regulator (CFTR) protein. Over 1400 mutations found in the gene contribute to the complexity of the CF phenotypes ranging from a classic multiorgan disease commonly involving respiratory, gastrointestinal and reproductive tract to mild and monosymptomatic presentations. Pilocarpine iontophoresis is considered as standard diagnostic test for CF, but it often fails in atypical forms of CF.
Methods: In order to provide an additional diagnostic test to assure the diagnosis and provide patients with a proper medical care, we performed a genetic testing on 16 adults suspected to have atypical form of CF. Following counselling, parents of patients with possible homozygote variant of mutations were tested. On a personal request testing was also performed in an adult sibling of a patient with two known mutations to investigate possible carrier hood. The allele specific polymerase chain reaction method (PCR) was used to detect 29 most common mutations in the cftr gene.
Results: The diagnosis was proved in 3 individuals, a homozygote for Δ F508, and two compound heterozygotes Δ F508/R1162X and Δ F508/3849+10kbC>T. In three cases only one mutation was found: I148T, 2789+5G>A and Δ F508 in a heterozygote form.
Conclusions: The genetic testing for CF is a valuable diagnostic tool in atypical forms of CF. Exclusion of possible differential diagnosis is warranted because of a variable CF phenotype. In cases where only one or no mutation was detected a necessity of whole gene sequencing is indicated to exclude rare mutations and polymorphisms that could be implicated in the pathogenesis of atypical CF.
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