Retinitis pigmentosa in abetalipoproteinemia: Effects of vitamin A.

Two patients with abetalipoproteinemia are shown to develop a serum vitamin A deficiency when maintained on a normal diet. This deficiency leads to a severe impairment of vision, including abnormalities of dark adaptation and the electroretinogram which involve both rod and cone receptor systems. Massive oral doses of vitamin A can reverse these abnormalities. Cone function recovers more rapidly than rod function after vitamin A therapy. The relationship between vitamin A and the retinitis pigmentosa which these patients develop is discussed.