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. Author manuscript; available in PMC: 2013 Jul 1.
Published in final edited form as: Liver Int. 2012 Apr 17;32(6):880–893. doi: 10.1111/j.1478-3231.2012.02794.x

Table 1.

Classification of Porphyria Cutanea Tarda

Type Percent of Cases Nature of Defect
I 75-80 Acquired defect leading to decreased activity of hepatic UROD [<25% normal activity]
II 20-25 Hereditary partial defect in UROD activity [~50% of normal] in all tissues. Other factors also required to produce clinical features
III <1 Very rare. Apparently inherited defect in an as yet unknown gene that leads to a secondary critical decrease in hepatic UROD activity.

UROD is uroporphyrinogen decarboxylase