 Levels of zinc-protoporphyrin, however did not decrease.X-linked sideroblastic anemia or "X-linked dominant erythropoietic protoporphyria", associated with ALAS2 (aminolevulinic acid synthase), has also been described.X-linked dominant erythropoietic protoporphyria (XDEPP) is caused by a gain of function mutation in the ALAS2 (5-aminolevulinate synthase) gene; that gene encodes the very first enzyme in the heme biosynthetic pathway.