Porphyrias are metabolic disorders that affect the biosynthesis of heme (a component of hemoglobin) and cause excessive production and excretion of porphyrins or their precursors. Porphyrins, which are present in all protoplasm, figure prominently in energy storage and use. Classification of porphyrias depends on the site of excessive porphyrin production; they may be erythropoietic (erythroid cells in bone marrow), hepatic (in the liver), or erythrohepatic (in bone marrow and liver). (See Types of porphyria.) An acute episode of intermittent hepatic porphyria may cause fatal respiratory paralysis. In the other forms of porphyrias, the prognosis is good with proper treatment.
Porphyrias are inherited as autosomal dominant traits, except for Günther’s disease (autosomal recessive trait) and toxic-acquired porphyria (usually from the ingestion of or exposure to lead). Menstruation commonly precipitates acute porphyria in premenopausal women.
Porphyrias are generally marked by photosensitivity, acute abdominal pain, and neuropathy. Hepatic porphyrias may produce a complex syndrome marked by distinct neurologic and hepatic dysfunction:
❑ Neurologic signs and symptoms include chronic brain syndrome, peripheral neuropathy and autonomic effects, tachycardia, labile hypertension, severe colicky lower abdominal pain, and constipation.
❑ During an acute attack, fever, leukocytosis, and fluid and electrolyte imbalance may occur.
❑ Structural hepatic effects include fatty infiltration of the liver, hepatic siderosis, and focal hepatocellular necrosis.
❑ Skin lesions may cause itching and burning, erythema, and altered pigmentation and edema in areas exposed to light. Some chronic skin changes include milia (white papules on the dorsal aspects of the hands) and hirsutism on the upper cheeks and periorbital areas.
Generally, diagnosis requires screening tests for porphyrins or their precursors (such as aminolevulinic acid [ALA] and porphobilinogen [PBG]) in urine, stool, or blood. Occasionally, skin biopsy may be performed. The protoporphyrin test measures porphyrins in the blood. Enzyme assays also help measure porphyrins. A urinary lead level of 0.2 mg/L confirms toxic-acquired porphyria.
Other laboratory values may include increased serum iron levels in porphy-ria cutanea tarda; leukocytosis, syndrome of inappropriate antidiuretic hormone, and elevated bilirubin and alkaline phosphatase levels in acute intermittent porphyria.
Treatment of porphyrias includes avoiding overexposure to the sun and using beta-carotene to reduce photosensitivity. Hemin (an enzyme-inhibitor derived from processed red blood cells) is given to control recurrent attacks of acute intermittent porphyria, Günther’s disease, variegate porphyria, and hereditary coproporphyria. A high-carbohydrate diet decreases urinary excretion of ALA and PBG, with restricted fluid intake to inhibit the release of antidiuretic hormone.
❑ Warn the patient to avoid excessive sun exposure, use a sunscreen when outdoors, and take a beta-carotene supplement to reduce photosensitivity.
❑ Encourage the patient to adhere to a high-carbohydrate diet.
❑ Administer beta-carotene and hemin as ordered.
❑ Tell the patient to avoid all alcohol and drugs that may precipitate an attack.
❑ Tell the patient to avoid skin trauma.
Review other book chapters online related to Porphyria:
Copyright notice for book excerpts: Copyright © 2008 Lippincott Williams & Wilkins. All rights reserved.
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Title: Handbook of Diseases Authors: Springhouse Publisher: Lippincott Williams & Wilkins Copyright: 2003 ISBN: 1-58255-266-5 
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