Heme also gives blood its color. Any circulating porphyrin the body doesn't use is excreted in urine and stool. When the body produces and excretes too much porphyrin, as happens with porphyria, not enough heme remains to keep a person healthy. Porphyria affects either the nervous system or the skin. When porphyria affects the skin, blisters, itching, swelling, and sensitivity to the sun can result.
Porphyria is an inherited condition.
Porphyria is diagnosed through tests on blood, urine, and stool.