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Alzheimer’s believed to be passed on from donors

There have been five cases of Alzheimer’s that are believed to have arisen as a result of medical treatments decades earlier, suggesting the disease could be transmitted between humans.

The new study provides the first evidence of Alzheimer’s disease in living people that appears to have been medically acquired from deceased donors and due to transmission of a toxic protein that causes the condition.

According to the University College London (UCL) and University College London Hospitals (UCLH) researchers, the findings may have important implications for understanding and treating Alzheimer’s disease.

Although the procedure that led to this transmission was stopped in the 80s, experts recommend medical procedures should be reviewed to ensure rare cases of Alzheimer’s transmission do not happen in the future.

There is no suggestion the protein (amyloid-beta) can be passed on in day-to-day life or during routine medical or social care.

Alzheimer’s is caused by the build-up of the proteins in the brain and usually occurs later in adult life with no specific family link, or more rarely it could be an inherited condition that occurs due to a faulty gene.

The people described in the study had all been treated as children with a type of human growth hormone taken from dead donors (cadaver-derived human growth hormone or c-hGH).

Between 1959 and 1985, this was used to treat at least 1,848 people in the UK and used for various causes of short stature, when a child or a teen is well below the average height of their peers.

But the treatment was withdrawn in 1985 after it was recognised that some c-hGH batches were contaminated with prions (infectious proteins) which had caused Creutzfeldt-Jakob disease (CJD) – a rare and fatal condition that affects the brain, in some people.

After that, c-hGH was replaced with a synthetic growth hormone that did not carry the risk of transmitting CJD.

This study reports on eight people referred to UCLH’s National Prion Clinic at the National Hospital for Neurology and Neurosurgery in London

The lead author of the research, Professor John Collinge, director of the UCL Institute of Prion Diseases and a consultant neurologist at UCLH, said: “There is no suggestion whatsoever that Alzheimer’s disease can be transmitted between individuals during activities of daily life or routine medical care.

“The patients we have described were given a specific and long-discontinued medical treatment which involved injecting patients with material now known to have been contaminated with disease-related proteins.

“However, the recognition of transmission of amyloid-beta pathology in these rare situations should lead us to review measures to prevent accidental transmission via other medical or surgical procedures, in order to prevent such cases occurring in future.

“Importantly, our findings also suggest that Alzheimer’s and some other neurological conditions share similar disease processes to CJD, and this may have important implications for understanding and treating Alzheimer’s disease in the future.”

The researchers previously reported that some patients with CJD due to c-hGH treatment (called iatrogenic CJD) also had prematurely developed deposits of the amyloid-beta protein in their brains.

In a 2018 paper they went on to show that archived samples of the hormone which were contaminated with amyloid-beta protein could transmit amyloid-beta to mice.

This latest study reports on eight people referred to UCLH’s National Prion Clinic at the National Hospital for Neurology and Neurosurgery in London, who had all been treated with c-hGH in childhood, often over several years.

Of those, five of them had symptoms of dementia, and either had already been diagnosed with Alzheimer’s disease or would otherwise meet the diagnostic criteria for this condition.

Another person met criteria for mild cognitive impairment.

These people were between 38 and 55 years old when they started having neurological symptoms.

Further tests supported the diagnoses of Alzheimer’s disease in two patients and was suggestive of Alzheimer’s in one other person.

Post-mortem analysis showed signs of Alzheimer’s in another patient.

Researchers say the unusually young age at which these patients developed symptoms suggests they did not have the usual Alzheimer’s which is associated with old age.

And in the five patients in whom samples were available for genetic testing, the team ruled out inherited Alzheimer’s disease.

Co-author Professor Jonathan Schott, UCL Queen Square Institute of Neurology, honorary consultant neurologist at UCLH, and chief medical officer at Alzheimer’s Research UK, said: “It is important to stress that the circumstances through which we believe these individuals tragically developed Alzheimer’s are highly unusual, and to reinforce that there is no risk that the disease can be spread between individuals or in routine medical care.

“These findings do, however, provide potentially valuable insights into disease mechanisms, and pave the way for further research which we hope will further our understanding of the causes of more typical, late onset Alzheimer’s disease.”

The findings are published in Nature Medicine.


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