Protracted neonatal hypertrypsinogenaemia, normal sweat chloride, and cystic fibrosis.

The cystic fibrosis (CF) clinical spectrum has greatly expanded in the past few years, including atypical forms with low sweat chloride concentrations. Two cases are presented which suggest that children detected by neonatal CF screening whose trypsinogen concentrations are still raised by the second month of age could, despite a negative sweat test, be affected by an atypical CF with fully expressed pulmonary involvement.