What is porphyria?

Porphyria is a general term for a group of disorders that affect the skin and nerves. People who have these disorders have one thing in common: Their bodies have problems making and using heme, a compound made in bone marrow and the liver. Heme is found in hemoglobin, a protein that allows red blood cells to carry oxygen throughout the body.

People with certain types of porphyria may develop skin blisters, swelling, and itching if they're exposed to the sun. Other types of porphyria can cause chest and abdomen pain, vomiting, and other unpleasant symptoms. Doctors usually perform an array of tests to diagnose porphyria.

Porphyria is a term that refers to a group of disorders-the porphyrias-that affect the nervous system or skin, or both. Each type of porphyria is due to the deficiency of one of the enzymes needed to make a substance called heme in the body. Enzymes are proteins that bring about certain chemical reactions in the body. The production of heme involves a series of eight different enzymes, each acting in turn.

Heme is a red pigment composed of iron linked to a chemical called protoporphyrin. Heme has important functions in the body. The largest amounts of heme are in the blood and bone marrow in the form of hemoglobin within red blood cells. Hemoglobin gives blood its red color and carries oxygen from the lungs to all parts of the body. In the liver, heme is a component of proteins that have many functions, including breaking down hormones, drugs, and other chemicals and generating high-energy compounds that keep the liver cells alive and functioning normally.

The body makes heme mainly in the bone marrow and the liver. The process of heme production is called the heme biosynthetic pathway. Each step of the process is controlled by one of eight enzymes. If any one of the enzymes is deficient, the process is disrupted. As a result, porphyrin or its precursors?chemicals formed at earlier steps of the process?may build up in body tissues and cause illness.

This answer is based on source information from the National Institute of Diabetes and Digestive and Kidney Diseases.