A case of human vitamin A deficiency caused by an inherited defect in retinol-binding protein without clinical symptoms except night blindness.

Two German siblings were found to suffer from night blindness and mild retinal dystrophy but no other clinical symptoms of vitamin A deficiency. Even though they had no detectable plasma retinal-binding protein (RBP) and their plasma retinol was exceedingly low, they showed normal physiologic functions and growth. Their RBP gene was found to harbor two point mutations. Their post-prandial plasma levels of retinyl esters were normal, and it is likely that they derived their tissue retinol from retinyl esters.