Porphyria cutanea tarda (PCT) is the most common human porphyria, due to hepatic deficiency of uroporphyrinogen decarboxylase (UROD), which is acquired in the presence of iron overload and various susceptibility factors, such as alcohol abuse, smoking, hepatitis C virus (HCV) infection, HIV infection, iron overload with HFE gene mutations, use of estrogens, and UROD mutation.
Mice modeling the hepatocutaneous porphyria, porphyria cutanea tarda (PCT), made possible the identification of the iron-dependent inhibitory mechanism of uroporphyrinogen decarboxylase (UROD) that leads to symptomatic PCT.
Porphyria cutanea tarda (PCT) is the only porphyria that has both genetic and/or environmental factors that lead to reduced activity of uroporphyrinogen decarboxylase in the liver.
A heterozygous UROD mutation causes half-normal levels of UROD activity systemically, which is a susceptibility factor but is not sufficient alone to cause type 2 PCT.
Acute intermittent porphyria causes kidney injury, whereas medical situations associated with end-stage renal disease, such as porphyrin accumulation, iron overload and hepatitis C, participate in the inhibition of uroporphyrinogen decarboxylase and predispose the individual to porphyria cutanea tarda.
In addition, we compared the frequency of the -163A highly inducible allele both in patients with symptomatic fPCT (n = 48) and in asymptomatic UROD gene mutations carrier relatives (n=54).
Porphyria cutanea tarda (PCT) is the most frequent type of porphyria worldwide and results from a catalytic deficiency of uroporphyrinogen decarboxylase (UROD), the fifth enzyme in heme biosynthesis.
Mutations of the UROD and hemochromatosis (HFE) genes are genetic factors in some PCT patients which can be mimicked in mice heterozygous for the Hfe and Urod null genes.
Hemochromatosis gene (HFE) mutations and the hepatitis C virus (HCV) are known risk factors for porphyria cutanea tarda (PCT), but interactions with erythrocytic uroporphyrinogen decarboxylase (UROD) have seldom been addressed.
UROD activity has a high diagnostic accuracy for differentiating the 2 PCT types, and a model that takes into account both clinical information and laboratory test results can be used to predict fPCT.
This study emphasizes the role of UROD mutations as a strong risk factor for PCT even in areas where environmental factors (hepatitis C virus) have been shown to be highly associated with the disease.
Recent advances in genetics and genomics have allowed DNA testing for porphyria cutanea tarda and are likely to be instrumental in developing improved, gene-based treatments and in finding genetic loci (in addition to uroporphyrinogen decarboxylase) involved in the clinical expression of this disease.
Erythrocyte UROD activity measurement and mutation analysis of the UROD gene were carried out in a cohort of 61 unrelated Spanish patients with PCT and 50 control individuals.