Porphyria cutanea tarda is the most common subtype of porphyria. The disorder results from low levels of the enzyme responsible for the fifth step in heme production. Heme is a vital molecule for all of the body's organs. It is a component of hemoglobin, the molecule that carries oxygen in the blood. The most common photocutaneous manifestations of PCT are due to increased mechanical fragility after sunlight exposure; erosions and blisters form painful indolent sores that heal with milia, dyspigmentation, and scarring. Other common features of PCT include hypertrichosis, sclerodermalike plaques that may develop dystrophic calcification, and excretion of discolored urine that resembles port wine or tea due to the porphyrin pigments present.
