Sweat potassium concentration may help to identify falsification of sweat test: A case report

OBJECTIVES: To document the relevance of sweat potassium concentration in a reported case of a white Caucasian 27-month-old boy who presented with non-specific respiratory symptoms and several abnormal sweat test results compatible with cystic fibrosis (CF). DESIGN AND METHODS: Repeated sweat tests using the Gibson-Cooke technique in the presence and absence of the mother. RESULTS: The high within- and between-test variability, the very low sweat potassium concentrations, several aspects of the family's history and a negative exhaustive genetic analysis to identify any CFTR mutation, raised suspicion for pediatric condition falsification. Two additional sweat tests performed in the absence of the mother were normal. CONCLUSION: CF diagnosis was then discarded and a Munchausen syndrome by proxy diagnosis was proposed.