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 secon d month of age could, despite a negative sweat test, be affected by an atyp ical CF with fully expressed pulmonary involvement.