Porphyrias

Causes

Porphyrias are inherited as autosomal dominant traits, except for Gunther's disease (autosomal recessive trait) and toxic-acquired porphyria (usually from ingestion of or exposure to lead). Menstruation often precipitates acute porphyria in premenopausal women.

Signs and symptoms

• Red urine
• Sensitivity to sunlight
• Crampy abdominal pain (may be extremely severe)
• Constipation
• Blister (bulla) formation on exposure to sunlight
• Skin swelling (edema) on exposure to sunlight
• Numbness or tingling
• Muscle pain
• Vomiting
• Pain in the limbs
• Muscle weakness or paralysis

Diagnosis

Generally, diagnosis requires screening tests for porphyrins or their precursors (such as aminolevulinic acid [ALA] and porphobilinogen [PBG]) in urine, stool, or blood or, occasionally, skin biopsy. A urinary lead level of 0.2 mg/L confirms toxic-acquired porphyria.

Other laboratory values may include increased serum iron levels in porphyria cutanea tarda; leukocytosis, syndrome of inappropriate antidiuretic hormone, and elevated bilirubin and alkaline phosphatase levels in acute intermittent porphyria.

Treatment

Treatment forporphyrias includes avoiding overexposure to the sun and using beta-carotene to reduce photosensitivity. Hemin (an enzymeinhibitor derived from processed red blood cells) is given to control recurrent attacks of acute intermittent porphyria, Giinther's disease, variegate porphyria, and hereditary coproporphyria. A high-carbohydrate diet decreases urinary excretion of ALA and PBG, with restricted fluid intake to inhibit release of antidiuretic hormone.

Alternative treatment

Acute porphyria attacks can be life-threatening events, so attempts at self-treatment can be dangerous. Alternative treatments can be useful adjuncts to conventional therapy. For example, some people may find relief for the pain associated with acute intermittent porphyria, hereditary coproporphyria, or variegate porphyria through acupuncture or hypnosis. Relaxation techniques, such as yoga or meditation , may also prove helpful in pain management .

Prevention

For the most part, the porphyrias are attributable to inherited genes; such inheritance cannot be prevented. However, symptoms can be limited or prevented by avoiding factors that trigger symptom development.

People with a family history of an acute porphyria should be screened for the disease. Even if symptoms are absent, it is useful to know about the presence of the gene to assess the risks of developing the associated porphyria. This knowledge also reveals whether a person's offspring may be at risk. Prenatal testing for certain porphyrias is possible. Prenatal diagnosis of congenital erythropoietic porphyria has been successfully accomplished. Any prenatal tests, however, would not indicate whether a child would develop porphyria symptoms; only that the potential is there.