Chronic metabolic alkalosis in an infant with cystic fibrosis.

A 6-month-old infant suffering from cystic fibrosis is reported. In spite of an apparently appropriate treatment and in absence of respiratory infection, the patient showed progressive anorexia, intermittent vomiting and weight loss. These non-specific signs and symptoms could all be explained by metabolic alkalosis and disappeared immediately after oral supplementation with sodium and potassium chloride. This unusual metabolic complication should be searched for in every cystic fibrosis infant with unexplained anorexia and failure to thrive.