| • | 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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