Alzheimer
's
, a disease that until now was only associated with old age or, in 2% of cases, with genetic inheritance, was the protagonist of a
scientific discovery
that questions the exhaustiveness of what was known until now about its origin in the brain. .
Research carried out in the United Kingdom and published by the journal
Nature
confirmed for the first time the
accidental transmission
, through medical treatment, of the protein that causes Alzheimer's.
They would be the first known cases of transmission of the disease.
For the authors of the study, this spread of Alzheimer's, although it occurred due to a totally "extraordinary" circumstance (due to its unusualness), shows the need for
extreme precautions
in medicine.
How extraordinary was that broadcast?
What was the treatment?
The first thing to understand is that, although it may seem like it, the researchers themselves clarify that
it is not an alarming announcement
.
The study found that
five patients
who had problems with short stature in childhood and were
treated with a contaminated growth hormone
- which was obtained from the brains of cadavers, something that stopped being done since 1985 -
ended up developing the
neuronal
disease without even having the associated age or genetic inheritance.
The hormone was contaminated with the protein
beta amyloid
, which when accumulated, is responsible for Alzheimer's.
These people were between 38 and 55 years old when they began to present neurological symptoms.
Why does protein become toxic?
People have about 86 billion neurons.
Some work especially with
memory
.
They connect to each other through a protein (amyloid precursor protein) that is replaced by a new one when it "wears out" and continues to fulfill its functions.
But that process of breaking down the old protein and eliminating it,
at some point stops working
.
Insoluble residues are formed, beta-amyloid, which stick together and cause this pathology.
When beta-amyloid accumulates outside neurons, it affects their interior, their skeleton, which is made up of the protein tau.
"Two tangles" of tau protein are formed, which are the ones that finish dissolving the neuron.
The investigation determined that this protein, which was transmitted during the procedure, spread decades later,
forming tangles that triggered the neurodegenerative disease
.
People with Alzheimer's can be due to the sporadic form of the disease, 98%, or to hereditary forms, 2%.
These Alzheimer's cases of the new discovery are “iatrogenic”, because their origin was in medical treatment.
A "contaminated" treatment
The growth hormone c-hGH, extracted from the pituitary glands of deceased people to treat problems of short height, was administered to 1,848 girls and boys in the United Kingdom between 1959 and 1985.
The suspension of its use in 1985 and its replacement with a synthetic hormone was because it was found that some batches contained infectious proteins that cause Creutzfeldt-Jakob disease, a brain disorder that often leads to
dementia
.
In 2017-2018, more than 30 years after this treatment was no longer indicated, the authors of the research analyzed stored samples of the growth hormone c-hGH and found that they were contaminated with the pathology associated with the amyloid beta protein, which It was still present despite all those decades stored.
When they administered them to mice, they saw that they developed Alzheimer's, which led them to wonder
what the evolution would have been of the girls and boys who received this old treatment
potentially contaminated with the amyloid beta protein.
"Our suspicion was that people exposed to that growth hormone who did not succumb to Creutzfeldt-Jakob disease and lived longer
could have ended up developing Alzheimer's disease
," one of the researchers explained at a press conference. authors, neurosurgeon John Collinge, from University College London.
Again, this transmission occurred after treatment with a now obsolete form of growth hormone.
In addition, it involved repeated procedures with this contaminated material - extracted from the pituitary gland of dead people - and for several years.
What the 8 cases studied reveal
A total of 8 patients were studied and five began to show symptoms of dementia between the ages of 38 and 55.
Currently they either have diagnosed Alzheimer's or
meet all the diagnostic criteria
for this disease.
Of the other three patients, one met the criteria for mild cognitive impairment.
The unusually early age at which these people developed symptoms suggests that they did not suffer from the usual Alzheimer's associated with old age, and in the five cases the existence of the gene that makes this disease hereditary in some cases was ruled out.
"
There is no indication that Alzheimer's disease can be transmitted between people
during activities of daily living or routine medical care. The patients we have described received specific medical treatment that was discontinued in 1985," Collinge clarified.
After this clarification, intended for the general public, the authors spoke to the medical community.
They agreed that the finding that Alzheimer's could be transmitted, even if it was in such an extraordinarily unusual way, should urge "to review measures to prevent accidental transmission through medical or surgical procedures, in order to prevent these cases." occur in the future.
The focus, mainly, would be the
instruments used in neurosurgery
, which should be ensured that they are not contaminated.
Concerns about the discovery
Tara Spiers-Jones, president of the British Society for Neuroscience, did not dispute the results of the study but did emphasize that
"it is not something that should worry people
. "
"There is no evidence that Alzheimer's disease can be transmitted between individuals in activities of daily living, nor is there evidence to suggest that current surgical procedures carry any risk of transmission of the disease," he noted.
Matías Baldoncini, neurosurgeon and professor at the UBA Faculty of Medicine, explained to
Clarín
the scope of this finding regarding the care that must be taken in the operating room.
"40 years ago (when the study cases take place) the asepsis and antisepsis techniques were different from those used today. The Creutzfeldt-Jakob disease virus, which was transmitted at that time, can be transmitted today if surgical instruments that are not adequately sterilized are used," he details.
But he clarifies that this "is practically impossible," because current techniques tend to eliminate all types of germs and, therefore,
"all types of contaminating factors
. "
Everything from the surgical material to the gauze, passing through the entire surgical field, is sterilized.
It is
a basic step in any surgery
, not just neurological ones.
Specifically for Alzheimer's, it reinforces that
it is not a contagious disease
.
"No doctor can become infected by examining a patient with Alzheimer's, even if he is hospitalized, or by operating on him. The research analyzed the possibility of contagion through an injection of hormones extracted from deceased people,
something that has been out of use for 40 years. years
," Baldoncini points out.
Neurologist Alejandro Andersson, a specialist in this neurodegenerative disease, tells this newspaper that what is relevant about the study is that it determines "that if you implant the toxic amyloid beta protein (extracted from a deceased person) into a patient, it replicates in their brain and causes Alzheimer's."
This activity is called
the prion mechanism
of disease
reproduction .
"It happens when a misfolded protein spreads that
misfolding
to a well-folded protein," he details.
This happened in the 5 cases found in the study.
"There should be no alarm today because growth hormone
is synthetic, it is manufactured in laboratories
," concludes Andersson.
ACE