Erythropoietic porphyria
Erythropoietic porphyria | |
---|---|
Specialty | Dermatology |
Erythropoietic porphyria is a type of
Types
There are three types:[2]
Name | OMIM
|
Gene |
---|---|---|
erythropoietic protoporphyria (EPP) | 177000 | ferrochelatase |
congenital erythropoietic porphyria or "Gunther's" (CEP)[3] : 526
|
263700 | uroporphyrinogen III synthase |
hepatoerythropoietic porphyria | 176100 | uroporphyrinogen III decarboxylase |
Presentation
X-linked dominant erythropoietic protoporphyria is a relatively mild version of porphyria with the predominant symptom being extreme photosensitivity causing severe itching and burning sensation of the skin due to the buildup of protoporphyrin IX. One possible treatment was discovered when treating an individual with supplemental iron for a gastric ulcer. Levels of free protoporphyrin decreased significantly as there was iron available for the FECH to produce heme. Levels of zinc-protoporphyrin, however did not decrease. [4][5]
Cause
Previously known mutations in the ALAS2 resulted in a loss-of-function mutation causing X-linked sideroblastic anemia. Erythropoietic protoporphyria (EPP) has similar symptoms as X-linked dominant erythropoietic 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 erythropoietic 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.
Diagnosis
The diagnosis is confirmed by finding increased red blood cell and plasma protoporphyrin levels. The peak plasma fluorescence occurs at 634 nm, following excitation at 410 nm.[citation needed]
See also
References
- ^ "OMIM - PORPHYRIA, CONGENITAL ERYTHROPOIETIC". Retrieved 2008-12-04.
- PMID 18537592.
- ISBN 978-0-7216-2921-6.
- PMID 18760763.
- ^ Online Mendelian Inheritance in Man (OMIM): 300752