Blood Disorders

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Porphyria

Porphyria is a group of different disorders caused by abnormalities in the chemical steps leading to the production of heme, a substance that is important in the body. The largest amounts of heme are in the blood and bone marrow, where it carries oxygen. Heme is also found in the liver and other tissues.

Multiple enzymes are needed for the body to produce heme. If any one of the enzymes is abnormal, the process cannot continue and the intermediate products, porphyrin or its precursors, may build up and be excreted in the urine and stool.

The porphyria disorders can be grouped by symptoms—whether they affect the skin or the nervous system. The cutaneous porphyrias affect the skin. People with cutaneous porphyria develop blisters, itching, and swelling of their skin when it is exposed to sunlight. The acute porphyrias affect the nervous system. Symptoms of acute porphyria include pain in the chest, abdomen, limbs, or back; muscle numbness, tingling, paralysis, or cramping; vomiting; constipation; and personality changes or mental disorders. These symptoms appear intermittently.

The porphyrias are inherited conditions, and the genes for all enzymes in the heme pathway have been identified. Some forms of porphyria result from inheriting an abnormal gene from one parent (autosomal dominant). Other forms are from inheriting an abnormal gene from each parent (autosomal recessive). The risk that individuals in an affected family will have the disease or transmit it to their children is quite different depending on the type.

Attacks of porphyria can develop over hours or days and last for days or weeks. Porphyria can be triggered by drugs (barbiturates, tranquilizers, birth control pills, sedatives), chemicals, fasting, smoking, drinking alcohol, infections, emotional and physical stress, menstrual hormones, and exposure to the sun.

Porphyria is diagnosed through blood, urine, and stool tests. Diagnosis may be difficult because the range of symptoms is common to many disorders and interpretation of the tests may be complex. Each form of porphyria is treated differently. Treatment may involve treating with heme, giving medicines to relieve the symptoms, or drawing blood. People who have severe attacks may need to be hospitalized.