Porphyria

Porphyria (por-FEER-ee-a) refers to a group of disorders that are genetic (hereditary). Common problems in porphyria include sensitivity to light, skin rashes, abdominal (ab-DOM-i-nal) pain, and discoloration of the urine.

What Is Porphyria?

When a person inherits a defective gene ^* from one or both parents, he or she may develop a form of porphyria. There are six classifications of this group of disorders. Some of them are rare. While exact numbers are not available, it is estimated that one person in 10,000 to 50,000 may be affected.

Undated engraving of King George III (1738-1820) of England, who reigned from 1760 to 1820 and is thought to have had porphyria.

Corbis/Betnman.

All six types of porphyria are a result of a problem in the chemical process by which the body makes heme, a compound that carries oxygen and makes blood red. Making heme requires eight different enzymes ^* . If any one of these enzymes fails, compounds that should be turned into heme instead build up in the body, especially in the liver ^* and in the bone marrow ^* , and cause problems. Some of these compounds are called porphyrins (POR-fi-rinz), which is where the disease gets its name. The different forms of porphyria occur from the failure of different enzymes.

Acute intermittent porphyria

This form of porphyria does not appear unless it is triggered by certain drugs, starvation or crash dieting, infection, and some hormones ^* in women. This form of porphyria is more common in women than in men. It usually occurs first during the young adult years. Symptoms include stomach pain, leg cramps, and muscle weakness. As its name indicates, it tends to occur from time to time (intermittently). In its most acute ^* forms, it can cause seizures ^* , paralysis ^* , depression ^* , and even hallucinations ^* or coma ^* . It is thought that King George III of England suffered from some form of porphyria.

Porphyria cutanea tarda (ku-TAY-ne-a TAR-da)

This is the most common form of porphyria and causes blisters ^* on the parts of the body that are exposed to sunlight. Some people with this form also develop liver disease. Substances that can cause an attack of this type of porphyria include alcohol, heavy intake of iron (iron overload), or the use of birth control pills. Porphyria cutanea tarda usually does not affect younger women. However, the increased use of substances that can trigger an attack, such as alcohol or birth control pills, has resulted in more younger women developing the disease. This type of porphyria is not inherited. Only about 20 percent of cases have a family history of the disease.

Protoporphyria

Protoporphyria (pro-to-por-FEER-ee-a) usually starts in childhood. The skin is extremely sensitive to sunlight, and painful rashes, redness, and itching may develop.

How Is Porphyria Diagnosed and Treated?

Diagnosis

Porphyria is diagnosed when an excess of porphyrins (compounds involved in making heme) is found in the urine. More laboratory tests help pinpoint specific forms of porphyria.

Treatment

Heme is given to treat acute intermittent porphyria. For porphyria cutanea tarda, in which there is an excess of iron in the body, the patient may be bled. A pint of blood is removed once or twice a week for several weeks, until iron levels drop to normal. Drug treatment for some forms of porphyria is available. Avoiding light and other substances that can trigger an attack is important for people who are susceptible to any form of porphyria. Sunscreens are not helpful for preventing skin eruptions. Sometimes, betacarotene (bay-ta-KAR-o-teen) is given to help with light sensitivity. Doctors recommend prevention of attacks by avoiding substances that trigger symptoms.