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
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.
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for Rare Disorders Inc. (NORD)
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