X-linked sideroblastic anemia or "X-linked dominant<unk>  protoporphyria", associated with ALAS2 (aminolevulinic acid synthase), has also been described. X-linked dominant<unk>  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. The mutation is caused by a frameshift mutation caused by one of two deletions in the ALAS2 exon 11, either c. 1706-1709 delAGTG or c. 1699-1700 delAT. This alters the 19th and 20th residues of the C-terminal domain thereby altering the secondary structure of the enzyme. The delAT mutation only occurred in one family studied whereas the delAGTG mutation occurred in several genetically distinct families. The delAGTG causes a loss of an α-helix which is replaced by a β-sheet. Previously known mutations in the ALAS2 resulted in a loss-of-function mutation causing X-linked sideroblastic anemia.<unk>  protoporphyria (EPP) has similar symptoms as X-linked dominant<unk>  protoporphyria but the mutation occurs as a loss-of-function in the FECH (ferrochelatase) enzyme; the very last enzyme in the pathway. All individuals studied presented symptoms without mutations in the FECH enzyme. The patterns of inheritance led the researchers to conclude the mutation must come from an enzyme on the X-chromosome with ALAS2 being the most likely candidate. X-linked dominant<unk>  protoporphyria is distinct from EPP in that there is no overload of Fe2+ ions. Additionally, unlike the other condition the arises out of a mutation of the ALAS2 gene, there is no anaemia. XDEPP is characterized by a buildup of protoporphyrin IX caused by in increased level of function in the ALAS2 enzyme. Because there is a buildup of protoporphyrin IX with no malfunction of the FECH enzyme, all the available Fe2+ is used in the production of heme, causing the FECH enzyme to use Zn2+ in its place, causing a buildup of zinc-protoporphyrin IX.
Erythropoietic porphyria
Hepatic porphyria
Hepatoerythropoietic porphyria
Acute intermittent porphyria
Variegate porphyria
Harderoporphyria
Porphyria
Pseudoporphyria