• | the most common porphyria |
• | presents 3rd or 4th decade |
acquired – (more common)
• | uroporphyrinogen decarboxylase deficiency (hepatocytes only) |
familial – autosomal dominant (less common)
• | uroporphyrinogen decarboxylase deficiency (in erythrocytes and hepatocytes) |
• | the majority of individuals who have inherited the enzyme defect do not develop PCT |
pathogenesis:
• | increased uroporphyrin in skin leads to photosensitization after absorbing light energy in soret band (400-410nm) |
• | alcohol, estrogen, iron, or hepatic disease precipitate all acquired forms and may unmask familial cases |
• | note: there is no evidence that by simply having PCT leads to liver damage |
iron:
• | hepatic iron overload is present in nearly every case of PCT and plasma iron is raised in up to 50% of patients |
• | studies suggest that iron in sporadic PCT is inactivating uroporphyrinogen decarboxylase, although the rarity of PCT in idiopathic hemochromatosis infers that this is not due to a direct toxic effect of the iron |
• | treatment for PCT is to phlebotomize (get rid of the iron) |
clinical:
• | hypertrichosis; sclerodermatous changes |
• | acral (photo-distributed) - tense bullae and erosions; milia and scarring (belay chronic and recurring blisters) |
histology:
• | blister goes thru papillary dermis, therefore scars |
• | bullae form subepidermally and are characterized by “festooning,” or upward protrusion of dermal papillae into the blister cavity and little or no dermal inflammatory infiltrate |
ddx:
• | pseudoporphyria, hereditary coproporphyria, EBA |
• | identical cutaneous findings |
• | rule out seizure history |
• | check ratio of URO to COPRO in urine (PCT = 8:1, VP = 1:1 (or COPRO>URO)) |
lab work up:
• | coral pink fluorescence of urine with Wood’s lamp (high false negative rate) |
• | check 24hr urine porphyrins (increased URO) |
• | plasma porphyrin level and fluorescence spectrum |
• | hepatitis panel (especially hepatitis C); if no alcohol or estrogen history, may want to rule out hepatoma with a scan |
treatment:
• | phlebotomy: 1 unit Q 2-4weeks until Hemoglobin/Hematocrit = 11/35 |
• | anti-malarials (low dose) |
• | eliminate iron, alcohol, and estrogen exposure |
• | broad spectrum sun screen |
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