Porphyria cutanea tarda (PCT) is a syndrome characterized by skin lesions occurring predominantly in areas exposed to sunlight. Skin changes include increased fragility to mechanical trauma, subepidermal vesicles or bullae, erosions, hyperpigmentation and hypopigmentation, hypertrichosis, sclerodermoid changes with associated scarring alopecia when the scalp or other hair-bearing areas are involved, dystrophic calcification, and milia.1 The syndrome is caused by a disorder of heme synthesis in which uroporphyrinogen decarboxylase (URO-D) is deficient.
Two forms of PCT have been described.2 The first is inherited as an autosomal-dominant trait, and the URO-D deficiency is evident in both hepatocytes and RBCs.2,3 The second type of PCT is called the sporadic form, and the URO-D deficiency is demonstrable only in hepatocytes.4 Both forms vary in their onset of symptoms; patients usually do not become symptomatic until after the fourth decade of life.1 Disorders associated with PCT to varying degrees include
Fivenson DP, King AJ. Porphyria Cutanea Tarda in a Patient With Agnogenic Myeloid Metaplasia. Arch Dermatol. 1984;120(4):538-539. doi:10.1001/archderm.1984.01650400120027