Chloride deficiency as a presentation or complication of cystic fibrosis.

Thirteen children with cystic fibrosis (CF), aged 1.5 months-15 years, had 18 episodes of hypochloraemia and metabolic alkalosis over the period 1983-1991. Five patients were not known to have CF prior to developing these electrolyte disturbances. There were two distinct clinical presentations: 5 patients had an acute isolated picture of heat exhaustion while 8 patients (all infants) had a more chronic course associated with failure to thrive. Many episodes were not associated with particularly high environmental temperatures, although most occurred during the summer and early autumn months. Serum electrolytes should be assessed regularly in children with CF, and this diagnosis should be considered in any infant presenting with unexplained hypochloraemic metabolic alkalosis.