Porphyria refers to a whole group of diseases causing the body to produce excess chemicals called porphyrin. Porphyrins are chemicals that make up most of the blood. called hemoglobin containing oxygen. Excess chemicals in the blood are excreted in the urine. Porphyria affects the skin or nervous system (brain, spinal cord), or both. Acute phase porphyria primarily causes neurologic symptoms. Porphyrias cause skin symptoms. Porphyria is less common. It can affect everyone