CYSTIC-FIBROSIS-LIKE DISEASE UNRELATED TO THE CYSTIC-FIBROSIS TRANSMEMBRANE CONDUCTANCE REGULATOR

Cystic fibrosis (CF) is considered to be a monogenic disease caused by molecular lesions within the cystic fibrosis transmembrane conductanc e regulator (CFTR) gene and is diagnosed by elevated sweat electrolyte s. We have investigated the clinical manifestations of cystic fibrosis , CFTR genetics and electrophysiology in a sibpair in which the brothe r is being treated as having CF, whereas his sister is asymptomatic. T he diagnosis of CF in the index patient is based on highly elevated sw eat electrolytes in the presence of CF-related pulmonary symptoms. The investigation of chloride conductance in respiratory and intestinal t issue by nasal potential difference and intestinal current measurement s, respectively, provides no evidence for CFTR dysfunction in the sibl ings who share the same CFTR alleles. No molecular lesion has been ide ntified in the CFTR gene of the brother. Findings in the investigated sibpair point to the existence of a CF-like disease with a positive sw eat test without CFTR being affected. Other factors influencing sodium or chloride transport are likely to be the cause of the symptoms in t he patient described.