Pseudo-Bartter syndrome: A CFTR-related disorder?

This case report presents a 14-month-old boy with a history of cystic fibrosis (CF) carrier status, diagnosed following a positive newborn screening for CF (CF-NBS), who developed symptoms suggestive of Pseudo-Bartter syndrome (PBS). Despite initial evaluations not meeting CF diagnostic criteria, subsequent investigations revealed an intermediate sweat chloride concentration, a second CFTR mutation, and CFTR dysfunction through rectal organoid morphology analysis (ROMA) consistent with CFTR-related disorder (CFTR-RD). This case raises important considerations regarding the diagnosis and management of CFTR-RD. PBS can be considered as a rare presentation of CFTR-RD and can occur in children with sweat chloride below the CF range. Functional testing of CFTR by ROMA enabled a more accurate diagnosis. Despite the negative work-up after CF-NBS, this infant developed CFTR-RD, but this should not be considered as a screen failure. Follow-up of children with CFTR-RD at a CF centre is preferred, because of the risk of developing CF.