Familial porphyria cutanea tarda. 50% of patients have only skin lesions on exposure to sunlight and skin trauma (e.g., edema, redness, bullae formation, scarring); also with abdominal pain (can mimic surgical abdomen) and neurologic sequelae. Condition has variable penetrance, with females less affected than males. Defect is in uroporphyrinogen decarboxylase; during attacks levels of porphyrins, porphobilinogen, and aminolevulinic acid are increased.