Learn More - Overview of the Porphyrias
The Cutaneous Porphyrias
Cutaneous porphyrias primarily affect the skin. Areas of skin exposed to the sun become fragile and blistered, which can lead to infection, scarring, changes in skin coloring (pigmentation), and increased hair growth. Cutaneous porphyrias include congenital erythropoietic porphyria, erythropoietic protoporphyria and X-linked protoporphyria, porphyria cutanea tarda, and hepatoerythropoietic porphyria.
Cutaneous Porphyrias: Porphyria Cutanea Tarda (PCT)
What is Porphyria Cutanea Tarda?
PCT is a deficiency of the enzyme uroporphyrinogen decarboxylase. Cutaneous blisters develop on sun-exposed areas of the skin, such as the hands and face. The skin in these areas may blister or peel after minor trauma. Increased hair growth, as well as darkening and thickening, of the skin may also occur. Neurological and abdominal symptoms are not characteristic of PCT.
Liver function abnormalities are common, but are usually mild. PCT is often associated with hepatitis C infection, which also can cause these liver complications. However, liver tests are generally abnormal even in PCT patients without hepatitis C infection. Progression to cirrhosis and even liver cancer occurs in some patients.
Who gets Porphyria Cutanea Tarda?
Porphyria cutanea tarda (PCT) is the most common type of porphyria, with a prevalence of approximately 1 in 10,000. PCT develops when the activity of the enzyme uroporphyrinogen decarboxylase (URO-decarboxylase) becomes severely deficient (less than 20% of normal) in the liver. In most cases these patients do not have URO-decarboxylase gene mutations and are said to have sporadic (or Type I) PCT (s-PCT), About 20 percent of cases have familial (or Type II) PCT (f--PCT). Such individuals have inherited a URO-decarboxylase gene mutation from one parent, which has reduced the amount of URO-decarboxylase in all tissues from birth. However, to develop symptoms, other factors must be present to reduce URO-decarboxylase level in the liver to less than 20% of normal. Such f-PCT patients may develop blisters at an early age or have relatives with the disease. Excess iron and multiple other susceptibility factors contribute to the development of PCT. These include use of alcohol or estrogens, smoking, chronic hepatitis C, HIV (human immunodeficiency virus), and mutations of the HFE gene which is associated with the disease hemochromatosis. Other factors remain to be identified. A URO-decarboxylase inhibitor generated only in the liver accounts for the severely deficient enzyme activity in PCT.
What causes Porphyria Cutanea Tarda ?
PCT develops when the activity of the enzyme uroporphyrinogen decarboxylase (URO-decarboxylase) becomes severely deficient (less than 20% of normal) in the liver.
How is Porphyria Cutanea Tarda Diagnosed?
The diagnosis of PCT can be made by finding a substantial elevation of porphyrins in urine or plasma. Elevations in feces may also be observed.
Patients with f-PCT usually have no family history of the disease, but can be recognized by finding half-normal URO-decarboxylase activity in red blood cells, or preferably by DNA studies.
- Also see FAQ: What diagnostic tests are available?
What are treatments for Porphyria Cutanea Tarda?
PCT, both familial and sporadic, can be treated with regularly scheduled phlebotomies (removal of blood) to lower the amount of porphyrins in the liver or a low dose regimen of hydroxychloroquine as well as removal of factors (for example, certain medications) that activated the disease. PCT is the most treatable of the porphyrias. Treatment seems to be equally effective in f-PCT and s-PCT. Factors that tend to activate the disease should be removed. Recurrences can be treated in the same manner.
