Porphyria Cutanea Tarda

Porphyrias are a spectrum of metabolic disorders arising from a defect or alteration of enzymes in the heme biosynthesis pathway which present with either neurovisceral symptoms, cutaneous symptoms, or a combination of the two. Porphyria cutanea tarda (PCT), the most common porphyria, is the result of a deficiency of the enzyme uroporphyrinogen decarboxylase (UROD). The hallmark of this disorder is photosensitivity. Hepatic UROD is tasked with the conversion of uroporphyrinogen III to coproporphyrinogen III, and failure to do so results in the accumulation of the preceding compounds in the liver that eventually appears in the plasma and urine.  Hepatoerythropoietic porphyria (HEP) is another rare form of porphyria which is clinically very similar to PCT but occurs due to homozygous mutation of UROD genes, whereas in PCT, the mutation in UROD gene, when present, is usually heterozygous. In this article, we discuss the different causes of UROD deficiency, along with clinically pertinent information for diagnosing and managing patients with PCT.