February 06, 2007



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August 16, 2006

Porphyria Cutanea Tarda


• Porphyrias: a group of diseases caused by inborn enzymatic defects in the heme biosynthetic pathway
• Most common type of porphyria is PCT
• PCT results from a deficiency of hepatic uroporphyrinogen decarboxylase activity
• Acquired and Familial forms exist
o Acquired PCT: most often precipitated by alcohol, Estrogens, oral contraceptives, certain environmental pollutants, and iron overloading with accompanying genetic factors
o Familial PCT: autosomal dominant
• Aside: PCT has been suggested in some of the vampire and werewolf legends, hence the character below


• Blistering in sun exposed areas (caused by the generation of peroxide by the UV excited porphyrins)
• Increased skin fragility
• Facial hypertrichosis (see all figures)
• Hyperpigmentation
• Sclerodermoid changes
• Dystrophic calcification with ulceration


• “Port-wine urine”: red-brown discoloration due to high levels of porphyrin pigments
• Urine with a bright pink fluorescence under a Wood's light
• Elevated urine uroporphyrin: coproporhyrin ratio- a ratio of 4:1 or more
• Quantitative assays of the various porphyrins must be performed to obtain a reliable diagnosis
• Biopsy specimens for direct immunofluorescence are taken from the edge of lesions


• Phlebotomy: iron removal because iron overload is one of the triggers of the disease. One unit of blood should be removed every 2 to 4 weeks until the hemoglobin drops to 10mirogm/dl or until the serum iron drops to 50micromg/dl.

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