Porphyria is rare hereditary or acquired metabolic disorder caused due to defective porphyrin metabolism. Porphyrin is a chemical in blood that helps hemoglobin to get saturated with oxygen which then circulates throughout the blood. Porphyria cutanea tarda (PCT) is one of its forms that affect the skin. It is the commonest of all forms of porphyrias.
PCT is characterized by eruption on skin caused due to exposure to sunlight. This condition is often colloquially referred to as Vampire disease because of its skin features such as blisters on face, hands and arm, fragile skin, crusts and scars on skin etc.
Treatment consists of frequent phlebotomy (removal of blood from vein to reduce the iron concentration), medicines and change in lifestyle. After treatment, prognosis is generally good.
What Causes Porphyria Cutanea Tarda?
Porphyria cutanea tarda is a form of porphyria that affects the skin. It occurs due to deficiency of a liver enzyme called uroporphyrinogen decarboxylase (UROD). The disease can be acquired or may be genetic in origin. PCT is prominently a liver porphyria as large quantity of porphyrin gets accumulated in liver in the active stage of the disease.
The disease becomes active when several acquired factors act together to cause deficiency of uroporphyrinogen decarboxylase enzyme in the liver. These factors are as follows; alcohol, smoking, estrogen, oral contraceptives, hepatitis C, HIV infection, exposure to environmental toxins and chemicals.
In majority of patients the disease is acquired. In few patients the disorder is hereditary. The common genetic causes include; strong family history of PCT, inherited deficiency of UROD enzyme and history of liver cancer in family.
A person is at greater risk of developing PCT if he smokes, drinks alcohol, or suffers from hepatitis C and HIV. PCT normally develops in middle age after 30 years. Both men and women are equally affected.
Signs And Symptoms Of Porphyria Cutanea Tarda
The symptoms of porphyria cutanea tarda are usually confined on skin. They may not develop immediately after sun exposure hence many people do not realize that triggering factor is exposure to sun.
Some of the common symptoms are as follows:
- Chronic recurring blisters on exposed parts of the body such as the scalp, face, neck, hands and arms.
- Severe itching on skin.
- Skin is sensitive to sunlight.
- Dark, thin and fragile skin.
- Increased growth of hair on face.
- Formation of crusts and scars.
- Ulceration on skin after minor injury.
- Red or Dark brown urine.
- Liver damage as PCT is often associated with hepatitis C infection.
Once the blisters start healing, the skin begins to peel off. The skin heals with scar formation.
Diagnosis And Treatment Of Porphyria Cutanea Tarda
Diagnosis of porphyria cutanea tarda is made with following test:
- Physical examination
- Family history
- Medical records
- Skin biopsy
- Blood test for porphyrin measurement.
- Urine and stool porphyrin estimate.
- If family history is present genetic testing for URDO deficiency.
Of all the different types of porphyria, porphyria cutanea tarda is one of the most treatable conditions. The main criterion of treatment is to stop and manage the symptoms. Change is lifestyle also has valuable implication in treating the illness.
Following are common treatment methods:
- Phlebotomy (a procedure in which certain amount of blood is removed from the vein). This will help to reduce the iron load on liver.
- Prompt withdrawal of offending agents such as alcohol, smoking, estrogen, iron supplements.
- Avoidance of use or exposure to pesticides.
- Pain medicines.
- Reduce mental and physical stress.
- Avoiding sunlight and sun exposure.
- Iron chelating therapy.
- Low dose choloroquine. This drug helps to remove excess of porphyrin from liver through urine.
Even after the treatment porphyrin level in blood is measured periodically. If there is a recurrence, prompt treatment is possible. The prognosis after treatment is good.