Porphyria cutanea tarda as the most common porphyria.

Porphyrias are an uncommon, heterogeneous group of metabolic diseases caused by inherited or acquired deficiency of specific enzymes in the heme biosynthetic pathway resulting in an excess of porphyrins (red-brown pigments) and their precursors. Accumulation of heme precursors, such as porphyrinogens that are spontaneously oxidized to porphyrins, is responsible for various clinical features. Porphyrias are classified into three groups: erythropoietic, hepatic and hepatoerythropoietic, depending on the primary organ affected. Porphyria cutanea tarda (PCT) is the most common porphyria, characterized by defective uroporphyrinogen III decarboxylase enzyme. There are three types of PCT with typical skin manifestations. Patients with PCT present with skin fragility, erosions, vesicles, bullae, and milia in sun-exposed areas of the skin, sometimes periorbital mottled hyperpigmentation and hypertrichosis, sclerodermoid changes and ulceration. We present the most common pathogenetic, clinical, diagnostic, and therapeutic features of PCT and other types of porphyria.