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.

Variegate (mixed) porphyria in a Nigerian girl

A fatal case of variegate (mixed) porphyria in an 11-year-old Nigerian girl is reported. She presented with severe abdominal pain, vomiting, constipation, quadriplegia and cutaneous bullous dermatosis. Remission was temporarily achieved with chlorpromazine, high carbohydrate diet and physiotherapy. She finally died of respiratory paralysis 17 months after diagnosis.

The porphyrias

The porphyrias are metabolic disorders in which there are excessive accumulation and excretion of porphyrins and porphyrin precursors. Each of the porphyrias has a specific enzyme defect in the pathway of heme biosynthesis that explains the pattern of biochemical abnormalities that occur. However, some patients have the enzyme defect but do not have clinical or biochemical manifestations, indicating that other factors (e.g., demand for increased heme biosynthesis) are also important in causing disease expression. The major clinical manifestations are neurologic dysfunction and photosensitivity. The precise cause of the neurologic dysfunction has not been defined, but the likely possibilities are overproduction of delta-aminolevulinic acid, which may act as a neurotoxin, or a deficiency of heme (or both). The cutaneous lesions in the porphyrias are due to the photo-sensitizing and other effects of porphyrins that are deposited in the skin or are circulating in dermal blood vessels. Therapy is directed to modify the biochemical abnormalities. Most importantly, intravenous administration of hematin is used in the treatment of acute attacks of neurologic dysfunction. Prevention remains a cornerstone in management of patients with porphyria, and those with gene defects should be counseled regarding factors that precipitate acute attacks.

Porphyrins in renal transplantation

The porphyrin status of 38 renal transplant patients was investigated using a sensitive thin-layer chromatographic assay. Abnormalities of porphyrin synthesis observed in patients on hemodialysis were generally reversed on receipt of a transplant with sustained good renal function. Urinary coproporphyrin levels and the creatinine clearance appeared directly related in both individual cases and generally, substantiating the theory that coproporphyrin is of renal origin. The pre- and postoperative porphyrin status of a unique patient with variegate porphyria who received a successful renal transplant implies that the excess urinary porphyrins and precursors excreted in the acute porphyrias are also of mainly renal, as opposed to hepatic origin. Furthermore, the posttransplant overproduction of porphyrins by a kidney from a normal donor suggests the existence of an endogenous porphyrogenic agent in the circulation of patients with acute porphyria.

A previous history of acute intermittent porphyria as a complication of obstetric anaesthesia

The administration of general anaesthesia for Caesarean section is described in a patient with an established biochemical diagnosis of acute intermittent porphyria. The technique used did not precipitate an acute exacerbation of the disease. Drugs associated with obstetric care are considered in the context of their use in porphyria.

[The hepatic porphyrias]

Among the different types of hepatic porphyrias, acute intermittent porphyria (AIP) and the group of chronic hepatic porphyrias (CHP) are most frequently seen in Europe. Both diseases are supposed to be inherited, but clinical manifestation mostly occurs following endogenous and especially exogenous stimulation. While recurrent attacks of abdominal and neuropsychiatric symptoms in AIP are frequently precipitated by therapeutic doses of commonly used drugs, the gradual development of porphyria cutanea tarda (PCT) from a clinically non-apparent type of CHP seems to be most commonly due to excessive and prolonged intake of alcohol. The characteristic and with regard to the laboratory findings important pathobiochemical features, the clinical symptoms, and the present therapeutic concepts of both disorders of hepatic porphyrin metabolism are discussed. The prognosis of hepatic porphyrias will be determined above all by early diagnosis of the metabolic disorder as well as by a profound medical information of the patient to avoid strictly all well-known exogenous factors which may initiate or exacerbate the disease.