Cystic fibrosis and normal sweat chloride values: a case-report

In a suggestive context, normal sit-eat chloride values (< 60 mmol/L) do no t always suffice to exclude the diagnosis of CF. Case-report A 19-year-old female presented with a diagnosis of bronchiectas is. Her past medical history was noteworthy for the onset of respiratory sy mptoms in the infancy, colonization of the respiratory tract by Pseudomonas aeruginosa for three years and previous treatment for allergic bronchopulm onary aspergillosis. She was heterozygote for the DeltaF 508 mutation of Me CFTR gene. Sweat chloride values it-ere repeatedly normal, ranging from 25 to 46 mmol/L. The diagnosis of CF was confirmed by the identification of a second CFTR mutation (D1152H) and the demonstration of typical nasal poten tial. Conclusion It is now estimated that approximately 2% of CF patients will pr esent an "atypical" phenotype with sweat chloride values < 60 mmol/L. For t hese patients, the diagnosis can be confirmed by the identification of a CF -causing mutation in each CFTR allele or in vivo demonstration of CFTR dysf unction by nasal potential difference study.