THE POLYPHYRIAS - CHARACTERISTICS AND LABORATORY TESTS

The term porphyria represents seven neuropathic and/or dermopathic dis eases caused by disturbances of the heme-forming system. Accumulation of the heme precursor, delta-aminolevulinic acid (delta ALA), is assoc iated with the neurologic manifestations, and accumulation of photorea ctive by-products, the porphyrins, causes cutaneous photosensitivity a nd dermopathic manifestations. The degrees of expression range from mi ld to severe, and acute episodes of neuropathic porphyrias can progres s to paralysis and life-threatening respiratory failure. Diagnostic la boratory tests include quantitation of delta ALA, porphobilinogen, and porphyrins in blood, urine, and feces and analysis of activities of e nzymes 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 examination s of persons who have experienced problematic chemical exposures. (C) 1996 Academic Press, Inc.