Cystic fibrosis in an infant presenting with metabolic alkalosis.

We recently had an opportunity to study a four-month-old boy with failure 
to thrive, hypochloremic metabolic alkalosis, high serum aldosterone values, and who 
was found to have cystic fibrosis. Children with cystic fibrosis have 
moderately elevated plasma renin and secondarily elevated serum aldosterone value. This 
is due to chronic sodium chloride loss through sweat. Our patient 
had high serum aldosterone values associated with only slightly elevated serum 
cortisol value. High serum aldosterone value increased further despite correcting conditions 
which stimulate aldosterone secretion. This suggests that long-standing salt depletion is 
not the only cause for abnormal renin-aldosterone system. 