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Porphyria Educational Services

Vol. 1 No. 8    February 1999
Bulletin Focus:  Porphyria Cutanea Tarda

Porphyria cutanea tarda which is better known as (PCT) is one of present eight known and confirmed types of porphyria. Unlike the other eight types of porphyria, PCT can be acquired as well as
inherited. Statistics among patients with a confirmed dx of PCT indicate that only about 20% have the inherited type, with the remaining the acquired form.

PCT a form of porphyria caused by a deficiency in activity of the enzyme uroporphyrinogen decarboxylase. Uroporphyrinogen decarboxylase is the fifth enzyme along the heme pathway
of eight enzymes which are responsible for the synthesis of heme. As aforementioned, PCT may be acquired, often in later life. The last of the PCT name, "tarda"  is the  Latin for the word meaning
late. Whether a person has the acuired form or the inherited form, either way the activity of uroporphyrinogen decarboxylase will be decreased to
approximately 50 of the normal value. Even with the decreased values it is thought that the majority of the time this
reduced level of activity will be sufficient to carry out normal heme synthesis.

When it is not sufficient, the activity is insufficient resulting in a decreased synthesis of heme. When this happens there is an accumulation of the products of the early
part of the heme biosynthetic pathway. The earlier stages of the this heme pathway continue to work normally. When the PCT is active the porphyrins accumulate in the site of synthesis.
Most synthesis occurs in the liver. From this point the excess porphyrins flow out  into the blood. From here the porphyrins may be either eliminated  into the urine,
or deposited in various tissues around the body. When  such porphyrins deposits  are found in the skin, they can absorb light. Most porphyrins are able to absorb light and store the energy in the form of
carbohydrates. However in PCT  the porphyrins which accumulate  are unable to store the energy of the light. This energy is released into the skin in photochemical reactions that cause
damage to the skin. When a PCT patient has continuous exposure to light, it will  lead to skin damage, which includes  blistering, and scarring. It is rare,  for patients to display the signs of PCT before their teenage
years, it is still possible.

Historically or typically, the  symptoms of the disease are first  observed when patients are in their 30's or 40's.

The most common symptoms or signs are the fragility and blistering of the skin. This  usually occurs on the backs of the hands and on the face. With out a doubt this is  probably because these two areas are most exposed
to sunlight. The blisters usually contain fluid. Following the breaking   of the blister, the underlying exposed tissues are usually slow to heal. Infections of the skin can and do occur.
Sometimes this will lead to scarring and changes in skin coloration. Patients often notice that their skin is unusually fragile. Even the slightest  bumps or knocks may lead to the upper surface of the
skin being scraped away.

Excessive growth of facial hair is another sign/symptoms of PCT. The reason for this hair growth is not  presently understood. However,once the PCT is under control, the hair can usually be easily and
effectively removed by conventional methods. Nair is a painless way, if a person is not otherwise sensitive to the materials used in the formula.

Certain factors are known to be important in precipitating the symptoms of PCT.
The drinking of alcohol has long been known to be a major trigger of PCT. It is particularly important to discontinue alcohol use, not only to enable effective treatment of the disease, but also because alcohol is well known to damage the liver. PCT is directly related to liver disease If PCT remains out of control, and the concentration of porphyrins continues to elevate in the liver, there is a progressive risk of direct damage to the
liver caused by the porphyrins. So, if a patient with PCT continues to drink alcohol, they will be at a double risk by damaging the liver both directly, and indirectly by prolonging the
overproduction of porphyrins.

Estrogens are also well known to precipitate the symptoms of PCT. Contraceptive pills with high estrogen contents, or post-menopausal women
who are taking estrogen for treatment of menopausal symptoms can cause serious problems for women.

Men are sometimes treated with estrogens (for example, for cancer of the prostate). It is not known precisely how estrogens influence the course of the
disease, but but it known by medical researchers  that they do.

Iron is another factor.  Iron will often cause the exacerbation of PCT. Often patients with blistering and skin disease caused by PCT are found to have extremely high levels of iron in their tissues.
Be careful of the use of Iron supplements. High iron levels are known to inhibit the activity of the enzyme uroporphyrinogen decarboxylase. Because of this, unusual diets which are very rich in iron, or iron
supplementation of the diet with tablets, are contra-indicated in PCT.

Industrial chemicals such as polychlorinated hydrocarbons are also bad in PCT.

The diagnosis of PCT is made by the demonstration of characteristically elevated porphyrin levels in the plasma and urine. Depending on circumstances, at times the activity of the defective enzyme
uroporphyrinogen decarboxylase is measured in red blood cells. If the activity is decreased in red blood cells, then generally the PCT has been inherited.

If it is normal in red blood cells, it is generally acquired. However, according the American Porphyria Foundation literature and research, this study is only indicated in certain specific circumstances (for
example, if two or more members of the same family have PCT, or for research purposes).

There are two steps in the  treatment of PCT.
The first is to search for and remove any of the factors which can exacerbate PCT [alcohol, chemical toxins, estrogen] and to avoid direct sunlight.
The second is a course of frequent phlebotomies, where approximately one pint of blood is removed at each phlebotomy.
The reason for this treatment is to decrease the amount of iron in the patient's body to the lower limit of normal.
Accordinging to the medical textbook, "The Metabolic Basis of Inherited Disease",
this happens because each time red blood cells are removed from the body, new red blood cells have to be synthesized, and this requires the use of
iron to synthesize the heme which is found in hemoglobin.

As a PCT patient your primary care physician should monitor your hemoglobin count and your iron count during therapy. According to the APF brochures on PCT, this  will also explain why the time
of treatment varies from patient to patient, because the amount of iron in the body varies at the start of the treatment. When the iron has been reduced to the lower limit of normal, the activity of the enzyme responsibile will generally improve to the level necessary
where there is no further abnormal accumulation of porphyrins. Because of this happening  the level of porphyrins in the blood and in the urine gradually reduces towards normal. As the porphyrins that were stored in the skin are released, the incidence
of photosensitivity decreases and new blisters are no longer formed. With a passage of time blisters will heal and scarring subside.

In PCT much of the scarring and changes in pigmentation may slowly become normal once again. In time the general texture  of the skin improves. PCT  patients eventually will no longer notice skin fragility.
As long as the porphyrin counts remain normal, there is no reason why patients should not expose themselves to the sun. Rarely, phlebotomy treatment by itself is insufficient to control the
disease. With some PCT patients phlebotomy may be an unwise choice of treatment due to other diseases, such as anemia or heart disease For these PCT patients low dose of chloroquine has often proved effective.
Chloroquine is the drug frequently used for the treatment of malaria. Chloroquine  it is thought, tends to bind porphyrins and increase their rate of excretion.
According to the APF, this treatment regime is generally safe, but there is a low incidence of damage to the retina of the eye with prolonged exposure to chloroquine.
Therefore it is advisable for PCT patients on chlorquine to receive periodic examinations from an ophthalmologist to guard against this possibility.

Once remission has been induced by either phlebotomy or chloroquine, the patient may remain in remission for two to eight or more years. This is  especially if precipitating factors are avoided.
It must be remembered however that it is not uncommon for PCT patients to experience a relapse with renewed photosensitivity and blistering. It is therefore generally advisable to monitor the plasma and urine
porphyrin levels at approximately six monthly intervals, even during remission. With this preventative approach, any increase in porphyrin levels can
usually be detected before the re-emergence of symptoms. Because of this, a PCT patient can have  early reinstitution of treatment followed by a more rapid remission.
PCT patients will have different degrees of photosensitivity, PCT patients will also have different severities of skin damage. In keeping with this PCT patients will also have different responses to
therapy and different durations of symptom free remissions.

The good news is that with proper treatment, PCT is not a progressive disease. It should be remembered that no two PCT patients will react or response in the same way.

Diana [AIP/PCT]