Since the seventeenth century, a strange evil has attacked, repeating itself through the generations, the descendants of a few families in remote villages on the Galician Costa da Morte. Doctors, during all that time, were unable to explain what was happening and local folklore attributed it to divine punishments or the spells of the meigas.
However, at the beginning of the 90s one of the affected people went to Manuel Arias Gómez , associate professor of Neurology at the University of Santiago de Compostela and Head of the Neurology Section of the Santiago de Compostela University Hospital Complex. Said patient, explains 20Minutos, presented the typical symptoms: “The first symptom is usually lack of balance to walk, followed by difficulty in articulating language, incoordination of extremities, loss of hearing acuity and atrophy of the tongue with mild dysphagia” .
An inherited ataxia
Arias was soon clear about what type of disease it was: “It is a degenerative disease that causes imbalance, of dominant inheritance (it can be transmitted with one of the affected parents) and that progresses slowly; it is, therefore, an ACS”.
These acronyms identify the spinocerebellar ataxias, a group within the hereditary ataxias that specifically affects the cerebellum and the spinal cord, which causes characteristic alterations in the strength, speed and dexterity of movement (and which are what the word ataxia).
This patient was soon followed by more, presenting “a very characteristic triad of symptoms,” consisting of “ataxia, hearing loss, and lingual atrophy with fasciculations.”
After the ataxia of Costa da Morte
Arias narrates that “In the following years the clinical phenotype was outlined and the first genetic studies were carried out , which were negative: it was already clear to me that it was not any of the known SCAs”.
“Subsequently, starting in 2005, we carried out an extensive field study, in which neurologists, neuropsychologists, molecular biologists, neuroradiologists, otolaryngologists and anatomopathologists participated, visiting numerous patients and relatives; the genetic linkage study revealed that all those affected they shared a particular region in the short arm of chromosome XX, where the NOP56 gene was located, which had a special mutation in one of its alleles : expansion of a hexanucleotide “, continues this neurologist.
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With these evidences, it was clear that the ataxia of the Costa da Morte was a unique and differentiated disease that was baptized as SCA36.
It is a disorder derived from a very specific mutation, which explains that it affects a very limited number of people and that most of them are in this Galician region . To get an idea of the figures, Arias details that in Galicia it is estimated that it affects about 150 people, with 300 more at risk of suffering from it.
Ataxia in Japan
At the same time, on the other side of the world, some Japanese doctors were also receiving some patients, inhabitants of the banks of the Ashida River (Hiroshima prefecture), with identical symptoms; and, like Arias, they decided to investigate to try to elucidate what was the nature of the underlying disease.
What they found was that the Ashida River ataxia was due to a mutation in the NOP56 gene, the same one that is altered in SCA36. Dr. Kobi Abe, responsible for this discovery, published his findings almost at the same time as Arias.
The strange gene that causes a rare disease in Galicia and Japan
Later, says Arias, “it was also described in some families in Taiwan, Italy, Poland, France and Albacete “; but never with the incidents (still very low) that occur on the Costa da Morte or in the Hiroshima prefecture.
Much has been theorized about a possible common origin of these two incarnations of the disease. Some voices have wanted to see the story of a sailor, Japanese or Galician, who had left descendants both in the Empire of the Rising Sun and in the land of the Suevi. However, Arias recalls, “the relationship of the Galician mutation with the Japanese one is not clear and it is thought that they could have arisen independently”.
Looking for treatments
Be that as it may, Arias, who this year was awarded by the Spanish Society of Neurology with the SEN award in recognition of his scientific work, continues to work with the SCA36, this time in search of treatments.
This disease causes patients to “fall easily, worsen with alcohol and require a wheelchair about 15-20 years after onset,” explains Arias, adding: “Some patients have moderate cognitive and emotional disorders.”
“At the moment preventive measures are indicated (avoid consumption of alcohol and toxic drugs for the nervous system and the ear), carry out physical exercise and use hearing protection in noisy environments”, he develops. However, there are hopeful horizons.
“Several lines of treatment are being investigated: some of them aimed at silencing the expansion of the gene , which is translated into the form of dipeptides that are toxic to neurons; also reducing neuronal death due to excitotixity, using special drugs (riluzole and derivatives) “, finally concludes Arias.