Porphyria cutanea tarda (PCT) is due to a defective enzyme in the liver (uroporphyrinogen decarboxylase). This is found in the liver and is involved in synthesis of the red pigment in blood cells (haem).
How common is porphyria cutanea tarda?
This type of porphyria occurs in an estimated 1 in 25,000 people, including both inherited and sporadic (noninherited) cases. An estimated 80 percent of porphyria cutanea tarda cases are sporadic. The exact frequency is not clear because many people with the condition never experience symptoms.
Causes of Porphyria Cutanea Tarda (PCT)
PCT occurs when uroporphyrinogen decarboxylase, a liver in the enzyme needed to synthesize heme, becoms inactived. This enyzme, which is used in the fourth step of the seven-step heme synthesis pathway, converts uroporphyrinogen III into coproporphyrinogen III by decarboxylating the acetic acid groups in the cytoplasm and converting them into methyl groups, which are transported back to the mitochondria. Inactivation of this enzyme can be triggered by iron, alcohol, estrogens, and infection with hepatitis C or HIV.
The skin, particularly on the backs of the hands and sometimes the face, becomes easily bruised and susceptible to fluid or blood-filled blisters.
Symptoms of Porphyria Cutanea Tarda (PCT)
People with porphyria cutanea tarda experience chronic, recurring blisters of various sizes on sun-exposed areas such as the arms, face, and especially the backs of the hands. Liver damage usually occurs, cirrhosis and even liver cancer may eventually develop.
Diagnosis of Porphyria Cutanea Tarda (PCT)
To diagnose porphyria cutanea tarda, a doctor tests the blood plasma, urine, and stool for increased levels of porphyrins.
Other important tests may involve checking the iron levels in the blood, looking for previous liver viral infections, and taking a history to detect aggravating drugs.
Treatment of Porphyria Cutanea Tarda (PCT)
Reduction of iron from the liver which is best done by therapeutic phlebotomy and by the iron chelator drug, Desferal; avoidance of inciting agents-especially alcohol, estrogens, polychlorinated aromatic hydrocarbons. Further, avoid sunlight or use skin creams containing dihydroxyacetone sun blocking agent when in sunlight.
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