Vitamin A (Retinol) Deficiency and Excess
Vitamin A deficiency has a number of characteristic clinical findings: night blindness (nyctalopia), bitot spots, dry / scaly skin (xerosis cutis), and keratomalacia / corneal liquefaction. Similarly, an excess of vitamin A can lead to a number of problems. A chronic vitamin A excess is characterized by dry skin, joint pain, pseudotumor cerebri, and hepatomegaly. An acute vitamin A toxicity presents with nausea, vomiting, and vertigo. A vitamin A excess during pregnancy is especially dangerous, as vitamin A is a potent teratogen.