PPOX and variegate porphyria: Variegate porphyria (VP), an autosomal dominant disease with incomplete penetrance, is characterized by photosensitivity and acute neurovisceral attacks and it results from the deficiency of protoporphyrinogen oxidase IX (PPO; E.C.1.3.3.4), the enzyme catalyzing the penultimate step of the porphyrin-heme biosynthetic pathway21–25.