Porphyria cutanea tarda is described as a light-sensitive skin condition2,3. With the disease, also comes a large amount of uroporphyrin excretion in the urinary system2. There are two types of porphyria which are the sporadic and familial type4. The sporadic type is classified by high levels of uroporphyrinogen in the liver whereas the familial type has a fifty percent deficiency of that exact enzyme. Porphyria is an autosomal dominant disorder that occurs in adults and children1,3. There are several factors that can induce this condition such as iron overload, aromatic chemicals, estrogens, HIV, hepatitis C, and mutation in the HFE gene2,4.
There will be an initial onset of light sensitivity later in the adult life along with large excretions of uroporphyrin in the urine for the sporadic type1,5. Other things that can occur on the skin are hyperpigmentation and hypertrichosis, and mechanical fragility is also a high risk3,5. The sporadic form can be associated with alcoholism and occasionally with exposure to agents such as estrogens3,4. There is an overload of iron that is present and this may be associated with liver damage or fibrosis1. The congenital form, also known as familial form, is associated with the deficiency of an enzyme called uroporphyrinogen III cosynthase1. The hepatoerythropoietic porphyria is a very severe, autosomal recessive form of porphyria that develops in infancy and is characterized by excretion of acetate-substituted porphyrins and accumulation of protoporphyrin in erythrocytes1,3,5.
With the familial form of porphyria there is reduced liver and red cell uroporphyrinogen decarboxylase activity and the sporadic forms of porphyria cutanea tarda2,4,5. There is impaired activity of an enzyme step in the heme synthesis inside the liver which has the ability to explain the overload of uroporphyrin4,5. There was also reduced hepatic uroporphyrinogen decarboxylase activity by fifty percent of the normal levels in the liver of porphyria cutanea tarda1,4. These reduced levels persisted long after the hepatic iron overload was relieved by venous treatments3,5. In hemolysates from some individuals with the familial form of porphyria there can be immunoreactive uroporphyrinogen decarboxylase levels that have been decreased to the same extent of catalytic activity2,4. In sporadic cases these values were within the normal ranges1,5.
The inherited mutations in the UROD gene cause about twenty percent of cases whereas the other eighty percent of the cases do not have this mutation and are categorized as sporadic3,5. As a result of having the rare UROD mutation in the familial form it is categorized as autosomal dominant whereas the sporadic form is autosomal recessive2. The sporadic form requires an additional mutational event to begin its cascade of events2. It appears that the reduced activity levels of uroporphyrinogen...