Of the various forms of porphyria, porphyria cutanea tarda is the most common. Although there is no porphyria registry in the U.S., the number of PCT sufferers in the U.S. is estimated at 1 in 25,000 to 50,000. Worldwide, the number of sufferers is highest in parts of Europe and Africa. PCT affects people of both genders and all races.
Definition
PCT is a chronic, autosomal dominant disorder. It is characterized by two traits: sunlight-sensitive skin and large quantities of uroporphyrin in the urine. It is often categorized in two types: sporadic and familial. In the sporadic, UROD uroporphyrinogen decarboxylase (UROD) deficiency occurs only in the hepatic cells (liver). The sporadic form (which accounts for about 80 percent of PCT cases) does not appear to be hereditary. In the familial, UROD occurs throughout the body. The familial form, accounting for about 20 percent of cases, is hereditary. UROD is a heme (blood) synthetic enzyme of the liver that involves the synthesis of blood's red pigment. The under-activity of this enzyme leads to an accumulation of porphyrins in the liver. This, in turn, leads to skin damage from the overproduced porphyrins, which are transported by the blood to the skin.
Signs and Symptoms
Typically, symptoms first appear in adulthood. The face, ears, forearms and backs of hands are especially sensitive and may be the first to exhibit signs. On these areas exposed to sunlight, chronic ulcerating lesions form, beginning as fluid-filled blisters. Sores may develop following relatively minor injuries. Where blisters heal, cysts may form. Changes in hair growth (increased facial hair) and coloring may also be noted. The skin around the eyes frequently develops mottled, brownish patches. In some cases, the skin becomes mechanically fragile, while in other cases, patches (especially on the neck, face and chest) may harden. Urine is typically darker than usual, having a reddish or tea-colored appearance. In severe cases, separation of the fingernails from the nail beds can occur.
Causes
Frequently, hepatitis viral infections are linked to PCT. Yet the underlying cause of PCT remains related to UROD activity during a critical point of hepatic heme synthesis. The disorder has also been associated with human immunodeficiency virus (HIV) infection. Lastly, there is evidence of a genetic link--the presence of one or two hereditary hemochromatosis genes.
Treatment
As with any chronic condition, a doctor's treatment is advised. However, there are things a patient can do to help manage the condition. Patients with PCT can minimize flareups by avoiding alcohol, iron supplements, exposure to sunlight, and estrogen and chlorinated cyclic hydrocarbons, including those found in pesticides. Patients with PCT can also take simple preventive measures, such as always wearing sunblock and cover-up as much as possible. Even the use of tanning creams containing dihydroxyacetone may help block the sun's rays.
To deal with the problem of an overabundance of iron, doctors may treat patients by phlebotomy, a method that gradually reduces the amount of iron in the blood by removing some of the blood (typically a pint). The process is generally repeated until the patient is borderline anemic. Also, due to the link between PCT and hepatitis C, a doctor may treat the patient for hepatitis C. Chloroquine and hydroxychloroquine (drugs used to treat malaria) are other medications a doctor may prescribe.
Related
Porphyrias are generally grouped as either acute (hepatic) or cutaneous (erythropoietic). Acute porphyrias primarily affect the nervous system. In addition to the physical symptoms affecting the skin, abdominal pain, vomiting, seizures, hallucination and paranoia can occur. The associated pain can be both acute and chronic. In cutaneous porphyrias, the skin is mainly affected and there may not be abdominal pain. The lack of abdominal pain is a key factor in distinguishing cutaneous forms of porphyria from acute forms.
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