By Disease Name > Porphyrias > Porphyria Cutanea Tarda

Porphyria Cutanea Tarda

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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
variegate porphyria:
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 Woods 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