Jose Decamps
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Why is porphyria cutanea tarda has photosensitivity?
If anyone knows it, please tell me. That was a question that appear in my Step 1 exam....
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| new_n_lost
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The most common presenting sign of PCT is fragility of sun-exposed skin after mechanical trauma, leading to erosions and bullae, typically on hands and forearms and occasionally on face or feet. Healing of crusted erosions and blisters leaves milia, hyperpigmented patches, and hypopigmented atrophic scars.
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| po
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got this info from here-
http://www.zevils.com/~matthewg/porphyria.html
Symptoms
Affected people get blisters on areas of the skin which are exposed to the sun. It also makes the skin sensitive to minor trauma. Crusting and scarring can also occur and will take a long time to heal. This skin damage happens because of the metabolite porphyrin. Porphyrins are one of the precursors of heme. Since there is a deficiency of this enzyme which is a part of the process which transforms porphyrins and the other heme precursors into heme, the porphyrins aren't getting used up. They accumulate in the liver and are transported to the skin by the blood plasma. When porphyrins are exposed to light and oxygen, they produced a charged, unstable oxygen which is harmful to the skin. PCT can also cause liver damage, including liver cancer and cirrhosis of the liver.
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| Jose Decamps
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Thank you guys......
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| Jose Decamps
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"Individuals with an enzyme defect leading to the accumulation of tetrapyrrole intermediates show photosensitivity-- that is, their skin itches and burns when exposed to sun light. ( Note: These symptoms are though to be due to the porphyrin-mediated formation of superoxide radicals from oxygen. These reactive oxygen species can oxidatively damage membranes and cause the release of destructive enzymes from lysosomes. Destruction of cellular components leads to the photosensitivity.)"
I just copied from the book....
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| po
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