Abstract



This is the first report of presumed sporadic Creutzfeldt-Jakob disease (sCJD) and Gerstmann-Sträussler-Scheinker disease (GSS) with the prion protein gene c.305C>T mutation (p.P102L) occurring in one family. The father and son were affected with GSS and the mother had a rapidly progressive form of CJD. Diagnosis of genetic, variant, and iatrogenic CJD was ruled out based on the mother’s clinical history, genetic tests, and biochemical investigations, all of which supported the diagnosis of sCJD. However, given the low incidence of sCJD and GSS, their co-occurrence in one family is extraordinary and challenging. Thus, a hypothesis for the transmission of infectious prion proteins (PrPSc) via microchimerism was proposed and investigated. DNA from 15 different brain regions and plasma samples of the CJD patient was subjected to PCR and shallow sequencing for detection of a male sex-determining chromosome Y (chr. Y). However, no trace of chr. Y was found. A long CJD incubation period or presumed small concentrations of chr. Y may explain the obtained results. Further studies of CJD and GSS animal models with controlled genetic and proteomic features are needed to determine whether maternal CJD triggered via microchimerism by a GSS fetus might present a new PrPSctransmission route.

Keywords:
Chromosome Y, Creutzfeldt-Jakob disease, Gerstmann-Sträussler-Scheinker disease, Microchimerism, PRNP, Prions, Transmission
Issue Section:
 Original Article

https://academic.oup.com/jnen/advance-article-abstract/doi/10.1093/jnen/nly043/5034506?redirectedFrom=PDF

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THE EPIDEMIOLOGY OF CREUTZFELDT-JAKOB DISEASE R. G. WILL 1984

THE EPIDEMIOLOGY OF CREUTZFELDT-JAKOB DISEASE

R. G. WILL

1984

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F. Familial Associations

The overall familial incidence of 6% in the retrospective section of this study contrasts with the estimated familial incidence of 15% in a review of the world wide epidemiology of C.J.D. (Masters et al., 1979a). In individual series higher figures are quoted with, for example, a familial incidence of 47% in Chile (Galvez et al., 1980) and 35% in Libyan born Israelis (Neugut et al., 1979). In a comprehensive retrospective survey of C.J.D. in France (Brown et al., 1979b), however, a 9% familial incidence was discovered, a figure comparable with this series. The low familial incidence may reflect either the difficulties of retrospectively obtaining an accurate family history or an artificially high familial incidence in relatively selected series due to extensive investigation of individual families.

The paradox of an apparently dominantly inherited condition (Masters et al., 1981a) which is yet transmissible is unresolved. Detailed investigation of individual families suggests that, if case to case transmission occurs, the incubation period must extend to decades (Masters et al., 1981a). Although this is compatible with the suspected incubation period of kuru (Gajdusek, 1979), the tendency for siblings to die at the same age rather than the same time (Masters et al., 1981a) supports the presence of a genetic influence. ***The discovery of a discordant identical twin pair in the present study suggests that even if there is an inherited susceptibility an environmental factor is necessary for the development of the condition. It further suggests that genetic integration of the agent is unlikely, in accordance with experimental evidence in which nuclear fractions are non-infectious (Millson et al., 1971) and vertical trans- mission has not been found in the laboratory (Amyx et al., 1981).

An unexpected but interesting finding in the context of familial associations is the group of nine patients with a first degree relative dying of a different 'degenerative' neurological condition. The extraordinary family with apparently dominantly inherited Alzheimer's disease and carcinoma of the colon is under investigation at another centre.

In other systematic studies of the epidemiology of C.J.D. an association with other neurological conditions has not been described but Masters (1981a) has reported four cases of C.J.D. occurring within four pedigrees of familial Alzheimer's disease. Adam et ale (1982) have described a family with a dominantly inherited neurological disorder sharing features of cerebral amyloidosis, spongiform encephalopathy and Alzheimer's disease. ***The relationship of C.J.D. to other degenerative neurological disorders may be a fruitful avenue of further epidemiological research.

CASE CONTROL STUDY

The objective of the case control study was to obtain quantitative data on putative risk factors and to identify potential common exposure to an environmental source of infection. The difficulties of such a study have been described by Bobowick et al. (1973) and Kondo and Kuroiwa (1982) in the only previous case control studies of C.J.D. In a rare condition such as C.J.D. it is difficult to obtain sufficient patient numbers to achieve statistically valid results. In this study 22 patients were included in the first 18 months, a number sufficient to exclude any ubiquitous risk factor but inadequate to distinguish relative risk. The case control study has, however, continued beyond the time limits of this analysis and to date over a hundred patients have been included.

The necessity of obtaining information at second hand introduces a potential source of error in the study of C.J.D. In this study the level of co-operation and detail of information was clearly enhanced by interviewing relatives prospectively and for this reason cases ascertained after death were not included in the prospective study. The checking of information given by relatives of control cases with the patients themselves suggested that the quality of information given at second hand was remarkably accurate.

The selection of controls is critical to the potential significance of a case control study. In this study age- and sex-matched controls were obtained from concurrent inpatients. Although in some cases the discovery of a suitable control proved both difficult and time-consuming, and in a few cases impossible, it was felt essential to persevere with the stated protocol in order to avoid the introduction of bias. Both previous case control studies were carried out retro- spectively and used 'healthy' and potentially over-matched controls.

Despite the differences between previous studies and the present case control study, the results were, almost without exception, both concordant and negative. No difference between patients and controls was discovered in past surgical or medical history, occupational history, educational history, eating habits or exposure to animals. Kondo and Kuroiwa (1982) discovered a correlation between physical injuries and the development of C.J.D. but could not exclude a methodological bias. No such correlation was discovered in this study and the subject was not examined in the study by Bobowick et ale (1973).

In the latter study the consumption of hog brains by patients was stressed but did not differ from the control group and in both this study and the study in Japan (Kondo and Kuroiwa, 1982) no dietary factory was related to increased risk of developing C.J.D.

***The successful oral transmission of C.J.D. and scrapie to primates (Gibbs et al., 1980) and the close resemblance between the properties of the transmissible agent in the two conditions (Gibbs and Gajdusek, 1976) has raised the possibility that the human disease is contracted from sheep. No direct evidence is available and the concept is based on inference and interesting but unconvincing anecdotes

(Alter et al., 1971; Lo Russo et al., 1980; Kamin and Patten, 1984). The patient discovered in this study who had never been known to eat meat suggests that eating scrapie infected meat cannot be the only source of C.J.D. in man. C.J.D. occurs in countries in which natural scrapie has not been observed (Galvez et al., 1980; Kondo and Kuroiwa, 1982) and no relationship was discovered in France (Chatelain et al., 1981) between the geographic distribution of scrapie and the incidence of C.J.D. A similar investigation could not be carried out in England and Wales as notification of scrapie to the Ministry of Agriculture is inconsistent and sheep farmers often destroy affected animals without seeking veterinary advice for fear of financial loss.

A detailed residential history was obtained in cases and controls. Although over-representation of cases was discovered in certain areas, similar but distinct areas of previous residence common to an apparent excess of controls was discovered. If C.J.D. does have a prolonged incubation period extending to decades the detailed study of residential history may, however, establish potential contact between individual cases which would be otherwise undetectable. The detailed study of individual cases in the prospective study has revealed the possibility of tenuous but extraordinarily coincidental contact between patients.

This may only be a reflection of intensive investigation, but if C.J.D. is transmitted by relatively minor surgical or dental procedures many years prior to death it is only by the systematic study of individual cases that potential cross-contamination may be discovered.

EVIDENCE FOR CASE-TO-CASE TRANSMISSION OF C.J.D.

The possible iatrogenic transmission of C.J.D. by neurosurgery, corneal transplantation and stereotactic electrodes has been suggested in the past (Duffy et al., 1974: Bernouilli et al., 1977; Masters et al., 1979a). In this series the close temporal relationship of neurosurgical procedures on two affected patients and three patients, unaffected at the time but who subsequently developed the disease is described. This provides strong circumstantial evidence of iatrogenic transmission by neurosurgery. Although sterilisation procedures have improved since the cases described, the unusual resistance of the agent and the recent description of probable neurosurgical transmission in France (Foncin et al., 1980) suggests that there is a continued risk of accidental transmission. However, brain biopsy to confirm the diagnosis of C.J.D. is now an unusual event and computed tomography has obviated the need for ventriculography.

The depth electrodes putatively responsible for one case of iatrogenic transmission in this series were inadequately sterilised in formalin and were subsequently used in over 200 patients. The neurosurgical instruments used in the cases of presumed neurosurgical transmission were sterilised using autoclaving procedures which were inadequate according to current advice (Gajdusek et al., 1978). However, despite detailed investigation, no cases other than those described above are known to have developed C.J.D. Thus, despite the possible implantation of the agent directly into the central nervous system, a large number of patients failed to develop the disease. This provides circumstantial evidence of an inherited susceptibility to the agent and suggests that cases of iatrogenic transmission may have occurred due to the unfortunate temporal proximity of susceptible individuals exposed to the agent.

In the close geographic group of three cases possible nodes of transmission can be suggested, either iatrogenic or through dental procedures, but these must remain conjectural. It is known, however, that the similar scrapie agent can be transmitted from the gums of animals (Adams and Edgar, 1978). Such close spatial clustering of cases is extremely unusual, being previously reported in England (Matthews, 1975a), Czechoslovakia (Mayer et al., 1977) and Hungary (Majtenyi, 1978), but not detected in the study of the epidemiology of C.J.D. in urban Paris (Cathala et al., 1978) where the incidence was found to be relatively high.

The occurrence of the disease in a patient who had contact with cases of familial C.J.D., but was not genetically related, has been described in Chile (Galvez et al., 1980) and in France (Brown et al., 1979b). In Chile the patient was related by marriage, but with no consanguinity, and had social contact with subsequently affected family members for 13 years before developing the disease. The contact case in France also married into a family in which C.J.D. was prevalent and had close contact with an affected member. In neither instance did the spouse of the non-familial case have the disease. The case described in this report was similarly related to affected family members and social contact had occurred for 20 years prior to developing C.J.D. If contact transmission had occurred, the minimum transmission period would be 11 years. Contact between sporadic cases has not been described and it is remarkable that possible contact transmissions have all been with familial cases. No method of transmission by casual social contact has been suggested.

 ***The occurrence of contact cases raises the possibility that transmission in families may be effected by an unusually virulent strain of the agent.

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 ***The occurrence of contact cases raises the possibility that transmission in families may be effected by an unusually virulent strain of the agent. ***



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TSS