Reye's syndrome: a case control study of medication use and associated viruses in Australia

Aspirin and Reye syndrome: a review of the evidence

Reye syndrome is an extremely rare but severe and often fatal disease. Death occurs in about 30-40% of cases from brainstem dysfunction. The disease typically is preceded by a viral infection with an intermediate disease-free interval of 3-5 days. The biochemical explanation for Reye-like symptoms is a generalized disturbance in mitochondrial metabolism, eventually resulting in metabolic failure in the liver and other tissues. The etiology of 'classical' Reye syndrome is unknown. Hypothetically, the syndrome may result from an unusual response to the preceding viral infection, which is determined by host genetic factors but can be modified by a variety of exogenous agents. Thus, several infections and diseases might present clinically with Reye-like symptoms. Exogenous agents involve a number of toxins, drugs (including aspirin [acetylsalicylic acid]), and other chemicals. The 'rise and fall' in the incidence of Reye syndrome is still poorly understood and unexplained. With a few exceptions, there were probably no new Reye-like diseases reported during the last 10 years that could not be explained by an inherited disorder of metabolism or a misdiagnosis. This may reflect scientific progress in the better understanding of cellular and molecular dysfunctions as disease-determining factors. Alternatively, the immune response to and the virulence of a virus might have changed by alteration of its genetic code. The suggestion of a defined cause-effect relationship between aspirin intake and Reye syndrome in children is not supported by sufficient facts. Clearly, no drug treatment is without side effects. Thus, a balanced view of whether treatment with a certain drug is justified in terms of the benefit/risk ratio is always necessary. Aspirin is no exception.

Reye's syndrome: the case for a causal link with aspirin

Reye's syndrome is a serious, acute encephalopathy that has been linked with aspirin (acetylsalicylic acid) use in children and teenagers <18 years of age. Although others may disagree, it is my belief that any objective analysis of published material in the last 20 years must conclude that there is a close link between the devastating encephalopathy Reye's syndrome and ingestion of aspirin during the febrile prodrome. The drug appears to act as a co-factor in susceptible individuals. Although some of the epidemiological data indicate an association between the two, the burden of evidence suggests actual causality and is both consistent and specific as well as strong and time related. Some of the evidence points to illness severity being dose related although it seems that in the presence of a viral infection, no dose of aspirin can be considered safe. No published work, using methodology that can be critically evaluated, has shown evidence to contradict these conclusions and they have been widely accepted. Since government health warnings were appended to aspirin-containing formulations, the decline in case numbers on both sides of the Atlantic has been nothing short of remarkable. Recent in vitro findings have pinpointed the site of action of the drug on the long chain hydroxyacyl-CoA dehydrogenase enzyme (a component of the mitochondrial trifunctional enzyme) and, even at therapeutic concentrations, oxidation is impaired in cultured fibroblasts from patients who have recovered from the disorder. This is quite unlike that seen in cells from normal controls. Even when major influenza outbreaks occur in the future, Reye's syndrome is preventable provided government health warnings are heeded and the cogent evidence set forth here is acted upon by the parents of feverish children and self-medicating teenagers.

Innate immune system regulation of nuclear hormone receptors in metabolic diseases

The immune system modulates a number of biological processes to properly defend against pathogens. Here, we review how crosstalk between nuclear hormone receptors and the innate immune system may influence multiple biological functions during an immune response. Although nuclear hormone receptor repression of innate immune responses and inflammation has been well studied, a number of new studies have identified repression of nuclear hormone receptor signaling by various innate immune responses. IFN regulatory factor 3, a key transcription factor involved in the induction of antiviral genes, may play a role in mediating such crosstalk between the innate immune response and nuclear receptor-regulated metabolism. This crosstalk mechanism is now implicated in the pathogenesis of atherosclerosis and Reye's syndrome and could provide an explanation for other pathogen-associated metabolic and developmental disorders.

A role for IRF3-dependent RXRalpha repression in hepatotoxicity associated with viral infections

Viral infections and antiviral responses have been linked to several metabolic diseases, including Reye's syndrome, which is aspirin-induced hepatotoxicity in the context of a viral infection. We identify an interferon regulatory factor 3 (IRF3)-dependent but type I interferon-independent pathway that strongly inhibits the expression of retinoid X receptor alpha (RXRalpha) and suppresses the induction of its downstream target genes, including those involved in hepatic detoxification. Activation of IRF3 by viral infection in vivo greatly enhances bile acid- and aspirin-induced hepatotoxicity. Our results provide a critical link between the innate immune response and host metabolism, identifying IRF3-mediated down-regulation of RXRalpha as a molecular mechanism for pathogen-associated metabolic diseases.

Is aspirin a cause of Reye's syndrome? A case against

Reye's syndrome was a rare disease which appeared suddenly in the early 1950s and disappeared just as suddenly in the late 1980s. An association between Reye's syndrome and the ingestion of aspirin (acetylsalicylic acid) was claimed, although no proof of causation was ever established. The presence of salicylates in the blood or urine of Reye's syndrome patients has not been demonstrated, and no animal model of Reye's syndrome has been developed where aspirin causes the disease. It is clear from epidemiological data that the incidence of Reye's syndrome was decreasing well before warning labels were placed on aspirin products. Reye's syndrome disappeared from countries where aspirin was not used in children as well as from countries which continued to use aspirin in children. Reye's syndrome was probably either a viral mutation which spontaneously disappeared, or a conglomeration of metabolic disorders that had not been recognized or described at that time.

Important role of prodromal viral infections responsible for inhibition of xenobiotic metabolizing enzymes in the pathomechanism of idiopathic Reye's syndrome, Stevens-Johnson syndrome, autoimmune hepatitis, and hepatotoxicity of the therapeutic doses of acetaminophen used in genetically predisposed persons

Upper respiratory tract febrile illnesses caused by various viruses, mycoplasma, chlamydia infections, and/or inflammatory diseases are usually observed a few days to a few (several) weeks before the onset of Reye's syndrome, Stevens-Johnson syndrome, autoimmune hepatitis (hepatotropic virus infections), or hepatotoxicity associated with therapeutic administration of acetaminophen in persons with varying degrees of deficits of important enzymatic activity. Activation of systemic host defense mechanisms by inflammatory component(s) results in depression of various induced and constitutive isoforms of cytochrome P-450 mixed-function oxidase system superfamily enzymes in the liver and most other tissues of the body. Because several cytochrome P-450 enzymes activities important for biotransformation of many endogenous and egzogenous substances show considerable variability between individuals, in some genetically predisposed persons, even the administration of therapeutic doses of a drug may result in serious clinical mishaps, if an important concomitant risk factor (eg, acute viral infection) is involved. Several inflammatory cytokines, such as interleukins, transforming growth factor beta1, human hepatocyte growth factor, and lymphotoxin, downregulate gene expression of major cytochrome P-450 enzymes with the specific effects on mRNA levels, protein expression, and enzyme activity observed with a given cytokine varying for each P-450 studied, thus eventually leading to metabolite-mediated adverse drug reactions and immunometallic diseases which sometimes result in tissue injury beyond the site(s) where metabolic bioactivation takes place. On the other hand, it must be emphasized that inhibition of metabolism of several drugs, as well as influence on the concentration and/or ratio of various cytokines in inflamed tissues, may exert beneficial effects in patients with different diseases, thus opening new therapeutic possibilities. Clinically relevant interactions may be exemplified by the effects of some fluoroquinolone antibiotics, such as pefloxacin and ciprofloxacin, which probably have a steroid-sparing effect in some patients with frequently relapsing nephrotic syndrome, and an increased bioavailability of several drugs following concomitant intake with freshly pressed grapefruit juice, eventually caused by inhibition of their metabolism, mediated mainly by CYP3A and specifically inhibited by naturally occurring flavonoids.

Whatever happened to Reye's syndrome? Did it ever really exist?

OBJECTIVE

Reye's syndrome (RS) appeared suddenly in the 1950s and disappeared almost as quickly in the late 1980s. A number of metabolic disorders were discovered in the 1980s that could completely mimic RS. This study was undertaken to reassess the original diagnosis of RS in light of newly described metabolic disorders.

INTERVENTION

The medical records of 26 patients who had survived RS and were originally studied in Australia in the 1980s were reexamined 10 yrs later, and families were interviewed to ascertain if the diagnosis had changed. The 49 original patients with RS from Australia were also reanalyzed using more precise diagnostic criteria for RS to ascertain how many of the patients would continue to fit the more precise diagnosis of RS.

MEASUREMENTS AND MAIN RESULTS

Of 26 original patients with RS who had survived, 18 (69%) were subsequently diagnosed as having other diseases, most commonly inborn errors of metabolism. The most commonly diagnosed metabolic disorder was medium-chain acyl-coenzyme-A dehydrogenase deficiency. Of the 18 patients rediagnosed with diseases other than RS, 15 (83%) are now known to have metabolic disorders. By using more precise diagnostic criteria for RS, none of the original 49 patients with RS could be diagnosed as having certain RS. Only six patients had probable RS, two patients had possible RS, 23 patients had unlikely RS, and 18 patients were excluded as RS cases.

CONCLUSION

With better diagnostic techniques and criteria, most patients originally diagnosed with RS are now known to have metabolic disorders. The disappearance of RS was probably related to the discovery and ability to diagnose inborn errors of metabolism that mimicked RS clinically, biochemically, and pathologically.

The changing clinical pattern of Reye's syndrome 1982-1990

OBJECTIVE

To describe trends in the clinical pattern of Reye's syndrome in the British Isles between 1982 and 1990; and to determine the relation between any changes and the June 1986 warnings against the use of aspirin in children.

DESIGN

Development, and application to reported cases, of a scoring system designed such that patients showing the typical clinical and pathological features of 'classical' Reye's syndrome scored highly. The relations between 'Reye scores' and a number of explanatory variables were explored using multivariable analysis.

SETTING

British Isles.

SUBJECTS

445 cases fulfilling the Reye's syndrome case definition reported to the surveillance scheme between January 1982 and December 1990.

MAIN OUTCOME MEASURE

Individual 'Reye score'.

RESULTS

Cases with high scores were more likely to have occurred in the 4 1/2 year period before June 1986 compared with the subsequent period (p < 0.006). Numbers of cases in the low and intermediate score categories declined by about 50% after June 1986, whereas those in the high category fell by 79%. High scorers were more likely to have received aspirin (p < 0.0001) and were older than intermediate and low scorers (p < 0.008). No relation was identified between score and season of onset.

CONCLUSIONS

The decline in Reye's syndrome after the aspirin warnings cannot be explained entirely, as has been proposed, by improved diagnosis of 'Reye-like' inherited metabolic and other disorders: this would not account for the greater decline of the high scoring subgroup which also contained those cases most likely to resemble 'classical' Reye's syndrome and to have received aspirin. This study provides further evidence for the role of aspirin in a subset of cases meeting the standard diagnostic criteria for Reye's syndrome and supports the need to consider this disorder as a heterogeneous group of conditions including Reye-like inherited metabolic disorders.

Reye's syndrome in Olmsted County, Minnesota: did it exist before 1963?

In this study, our goals were to determine whether Reye's syndrome existed before the first published report of this entity in 1963 and to describe the long-term incidence and trend of this syndrome. Medical and pathologic records and pathologic specimens for Mayo Clinic patients, including those who were residents of Olmsted County, Minnesota, were reviewed through the facilities of the Rochester Epidemiology Project. On review, 12 cases were identified for the period 1920 through 1962; 2 of these cases were in Olmsted County residents. Of the 12 cases identified before 1963, 10 were in patients younger than 5 years of age. In addition to the aforementioned two cases, five others in Olmsted County were diagnosed between 1963 and 1989. Incidence rates were computed for the Olmsted County population. The number of cases and rates per 100,000 persons younger than 18 years of age in that population were 2 cases (0.3) for 1920 through 1962, 4 cases (0.7) for 1963 through 1980, and 1 case (0.4) for 1981 through 1989. Although cases found during the earlier periods may have included disorders that mimic Reye's syndrome, the recommended criteria from the Centers for Disease Control were applied to review of medical records and supported by pathologic findings in the liver. The data showed an age distribution tending toward young patients and no seasonality of occurrence. The incidence rates in Olmsted County, Minnesota, showed an increase for 1963 through 1980 over previous decades, followed by a decrease. The small numbers preclude any conclusion about trends in the incidence rates.