PCT manifests when hepatic UROD activity is <20% of normal.1 As porphyrins accumulate in the liver, they are transported to the skin, leading to phototoxicity as light exposure causes the porphyrins to release photons.1 Subsequently, patients develop blisters on sun-exposed areas of their skin, particularly the hands, face, neck, and forearms. These areas are also prone to blisters and peeling after mild trauma. When the lesions scar, they may resemble systemic scleroderma. In some cases, lesions become painful. Patients may also have abnormal hair growth, skin thickening, and hypopigmentation. PCT is diagnosed when elevated porphyrins are detected in the plasma. Urine and fecal studies can confirm the diagnosis when they show similarly elevated porphyrin levels, with urine typically showing excess uroporphyrin and 7-carboxylate porphyrin and feces showing excess isocoproporphyrin.6 Patients with a PCT diagnosis should be tested for HCV if their status is unknown. Photo Credit: Dr Harout Tanielian/Science Source.