The polyphyrias: Characteristics and laboratory tests

The term porphyria represents seven neuropathic and/or dermopathic diseases caused by disturbances of the heme-forming system. Accumulation of the heme precursor, delta-aminolevulinic acid (delta ALA), is associated with the neurologic manifestations, and accumulation of photoreactive by-products, the porphyrins, causes cutaneous photosensitivity and dermopathic manifestations. The degrees of expression range from mild to severe, and acute episodes of neuropathic porphyrias can progress to paralysis and life-threatening respiratory failure. Diagnostic laboratory tests include quantitation of delta ALA, porphobilinogen, and porphyrins in blood, urine, and feces and analysis of activities of enzymes of the heme-forming system. Both inheritable and noninheritable forms of porphyria can be induced by toxic chemicals, and, therefore, tests for porphyria are becoming included increasingly in examinations of persons who have experienced problematic chemical exposures. (C) 1996 Academic Press, Inc.