MODEL RELEASED. Porphyria on a patient's face. Porphyria is the term given to a group of disorders where an enzyme deficiency causes a build-up of porphyrin chemicals in the body. Porphyrins are normal body chemicals that are required to synthesize other substances, such as haem, a component of haemoglobin found in red blood cells. The skin of patients with porphyria often becomes photosensitized and burns or blisters easily. Porphyria also causes dark coloured urine due to excess excretion of porphyrins. Treatment of porphyria depends on the enzyme involved, but may include drugs or restricting sun exposure.