| Porphyriaa | Affected Enzyme | Known Mutations | Inheritance | Classification | Principal Clinical Features |
|---|---|---|---|---|---|
| X-linked protoporphyria (XLP) | δ-Aminolevulinic acid (ALA) synthase-erythroid specific form (ALAS2) | 4 (gain of function) | Sex linked | Erythropoietic | Nonblistering photosensitivity |
| δ-Aminolevulinic acid dehydratase porphyria (ADP) | ALA dehydratase (ALAD) | 10 | Autosomal recessive | Hepaticb | Neurovisceral |
| Acute intermittent porphyria (AIP) | Hydroxymethylbilane synthase (HMBS) | >400 | Autosomal dominant | Hepatic | Neurovisceral |
| Congenital erythropoietic porphyria (CEP) | Uroporphyrinogen III synthase (UROS) | 48 | Autosomal recessive | Erythropoietic | Neurovisceral |
| Porphyria cutanea tarda (PCT) | Uroporphyrinogen decarboxylase (UROD) | 121 (includes HEP) | Autosomal dominantc | Hepatic | Blistering photosensitivity |
| Hepatoerythropoietic porphyria (HEP) | UROD | — | Autosomal recessive | Hepaticb | Blistering photosensitivity |
| Hereditary coproporphyria (HCP) | Coproporphyrinogen oxidase (CPOX) | 64 | Autosomal dominant | Hepatic | Neurovisceral; blistering photosensitivity (uncommon) |
| Variegate porphyria (VP) | Protoporphyrinogen oxidase (PPOX) | 174 | Autosomal dominant | Hepatic | Neurovisceral; blistering photosensitivity (common) |
| Erythropoietic protoporphyria (EPP) | Ferrochelatase (FECH) | 189 | Autosomal recessive | Erythropoietic | Nonblistering photosensitivity |
a Porphyrias are listed in the order of the affected enzyme in the heme biosynthetic pathway.
b These porphyrias also have erythropoietic features, including increases in erythrocyte zinc protoporphyrin.
c UROD inhibition in PCT is mostly acquired, but an inherited deficiency of the enzyme predisposes in familial (type 2) disease.
Source: Reproduced with permission from Kang S, Amagai M, Bruckner AL, Enk AH, Margolis DJ, McMichael AJ, Orringer JS, eds. Fitzpatrick's Dermatology. 9th ed. New York, NY: McGraw Hill; 2019, Table 124-1.