Notes on histopathological studies of the nervous system in experimental porphyria

No evidence of unequivocal myelin degeneration has been found in rabbits, fowls and rats intoxicated with allyl-isopropyl-acetamide. In one rabbit, myelin changes were observed, but these were considered to be atypical of true myelin degeneration and could be attributed to causes other than the direct action of the drug.

DIFFUSE DEGENERATION OF CEREBRAL WHITE MATTER RESEMBLING SOCALLED BINSWANGER'S DISEASE AND SYMMETRICAL NECROSIS OF THE GLOBUS PALLIDUS ASSOCIATED WITH ACUTE PORPHYRIA AND CEREBRAL ATHEROSCLEROSIS

A 59-year-old woman admitted to hospital in coma also showed generalized muscular rigidity and porphyria. After two days she became fully conscious but the muscular rigidity increased and persisted until death occurred 12 weeks later. The brain showed diffuse degeneration of the white matter; symmetrical necrosis of the globus pallidus was associated with severe localized atherosclerosis. The lesions probably resulted from the combined effects of porphyria and atherosclerosis. It is suggested that in later life unusual cerebral lesions may occur with porphyria because of associated atherosclerosis. The porphyria may be overlooked clinically.

Anesthetic considerations in porphyrias

Four hereditary types of porphyria are now classified as acute porphyrias. Enzymatic defects result in accumulation of porphyrin precursors (usually ALA and PGB). The quantity of these precursors may be normal or slightly increased in latent periods but increase to toxic levels during a porphyric crisis. Iatrogenic induction of ALA synthetase by administration of certain triggers (classically barbiturates) is only one of several factors which contribute to porphyric crisis. Signs and symptoms of acute porphyric attack consist primarily of neurologic dysfunction, which occurs secondary to neurotoxicity of ALA or diminished intraneuronal heme levels. Appropriate anesthetic management of porphyria requires knowledge of the type of porphyria (acute vs non-acute), assessment of latent versus active (crisis) phase, awareness of clinical features of porphyric attack, and knowledge of safe pharmacologic intervention.