Letter: Skin wrinkling in cystic fibrosis.

The water-binding capacity of a protein is minimal at its isoelectric point 
(pH 3.5 - 5 for the keratins making up the horny 
layers) and increases with increasing divergence from the isoelectric point. It 
is for this reason that normal palmar skin wrinkles after moderate 
immersion in warm water, especially if it is soapy (pH 8 
or more). However, in patients with cystic fibrosis it is the 
increased salt content of the sweat rather than the pH difference 
which increases the water-binding capacity of the keratin, and is responsible 
for the wrinkling in these patients. 