by Five cases of Alzheimer’s believed to have developed as a result of medical treatment involving donor hormones decades earlier have been identified.
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 is caused by the transmission of a toxic protein that causes the condition.
According to University College London (UCL) and University College London Hospitals (UCLH) researchers, the findings could have important implications for understanding and treating Alzheimer’s disease.
Although the procedure that caused this transmission was stopped in the eighties, experts suggest that medical procedures should be reviewed to ensure that rare cases of Alzheimer’s transmission do not occur in the future.
There is no suggestion that the protein (amyloid-beta) can be passed on in daily life or during routine medical or social care.
Alzheimer’s is caused by the build-up of proteins in the brain, and usually occurs later in adulthood with no particular family link, or more rarely it may be an inherited condition caused by a faulty gene.
The people described in the study were all treated as children with a form 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 was used for a variety of reasons related to short stature – when a child or teenager is well below the average height of their peers.
But the treatment was withdrawn in 1985 after some batches of c-hGH were found to be contaminated with prions (infectious proteins) which caused Creutzfeldt-Jakob disease (CJD) – a rare and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.
Lead author of the research, Professor John Collinge, director of the UCL Institute of Prion Diseases and consultant neurologist at UCLH, said: “There is no suggestion that Alzheimer’s disease can be transmitted between individuals during activities of daily living or medical procedures. care.
“The patients we described were given a specific long-term medical treatment, which involved injecting patients with material now known to be contaminated with disease-related proteins.
“However, recognizing the transmission of amyloid-beta pathology in these rare cases should lead us to review measures to prevent accidental transmission through other medical or surgical procedures, in order to prevent such cases in the future .
“Importantly, our findings also suggest that Alzheimer’s and several other neurological conditions share disease processes similar 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 (known as iatrogenic CJD) had prematurely developed deposits of the amyloid-beta protein in their brains.
In a 2018 paper they went on to show that archival samples of the hormone that were contaminated with amyloid-beta protein could transmit amyloid-beta to mice.
This latest study reports on eight people referred to the UCLH National Prion Clinic at the National Hospital for Neurology and Neurosurgery in London, all treated with c-hGH in childhood, often over several years.
Five of them had signs of dementia, and either already had Alzheimer’s disease or would meet the diagnostic criteria for this condition.
Another met the criteria for mild cognitive impairment.
These people were between 38 and 55 years old when they started having neurological symptoms.
Additional tests supported the diagnoses of Alzheimer’s disease in two patients, and one other person was diagnosed with Alzheimer’s.
A 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 typical Alzheimer’s associated with old age.
And of the five patients who had samples available for genetic testing, the team ruled out inherited Alzheimer’s disease.
Co-author Professor Jonathan Schott, UCL Queen’s Square Institute of Neurology, honorary consultant neurologist at UCLH, and chief medical officer at Alzheimer’s Research UK, said: “It is important to point out that the circumstances by which we believe these people developed Alzheimer’s disease tragically. very unusual, and to emphasize that there is no risk that the disease could be spread between individuals or in normal medical care.
“However, these findings provide potentially valuable insights into disease mechanisms, and pave the way for further research that we hope will improve our understanding of the causes of more typical Alzheimer’s disease, later.”
The results are published in Nature Medicine.
