Penicuik Siblings With Rare Chromosomal Disease Search Database For Match
IMAGINE discovering that your child was born with a genetic defect so rare that doctors know of no other confirmed cases.
This was the scenario Kenny and Crystal Arnott of Penicuik faced when their daughter Lily arrived five years ago.
The couple had suffered a series of miscarriages which genetic testing ultimately linked to a chromosomal defect carried by Ms Arnott, known as a “balanced translocation”.
Normal human cells contain 23 pairs of chromosomes, each made up of two strands of DNA, one inherited from our mother and the other from our father.
In a balanced translocation, a section of genetic material changes places between the chromosomes.
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Although normally harmless, it can lead to problems with conception and increases the risk of an ‘imbalanced translocation’ in the offspring, which means they have duplicate or missing pieces of the chromosome, which can lead to learning disabilities. , developmental delays and health problems.
Genetic testing after Lily was born established that she had an extra strand of chromosome – in addition to the 46 strands that normally make up the 23 pairs – which included a large portion of her maternal chromosome 21 and a shorter portion of the maternal chromosome. 18.
Her younger brother, Benjamin, three, has the same unusual arrangement that has so far not been identified in any other patient whose details are recorded in UK or international databases.
Although it shares some similarities with Down syndrome, where people carry three copies of chromosome 21, the extra portion of DNA found in Arnotts’ children is not the part considered critical for causing the associated medical problems. , such as hearing loss and early onset. dementia, and doctors can offer little advice on how their conditions might progress.
“Our children do not have any of Down’s facial features,” said Mr Arnott, 42, from Glasgow.
âThey take them down the medical path like it’s Down, but they’re kinda on a wing and a prayer because it’s an information void. They just don’t know.
âOur two children are developmentally delayed. They don’t speak – or they speak a word or two.
âMy five-and-a-half-year-old daughter just graduated from elementary school and still wears diapers. She has hypermobility and therefore has severe pain in her joints.
“They both still use strollers, and my son has a lot of lung infections – he’s hospitalized all the time with croup.”
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The Arnott’s are one of 684 Scottish families who have signed up for the Surrey-based Unique charity, whose world-renowned database helps locate and match families with extremely rare chromosomal and genetic disorders in the UK. or abroad.
Mr Arnott, head of global business development for a hotel company, said finding a match “would be huge”.
“We have nothing to assess our children,” he said. “If you had another family, that would give you a better idea of ââwhat the milestones might be, because – whatever the milestones for a ‘normal’ child – they came out the window soon enough for us.
“My kids didn’t walk until they were two and a half, they didn’t look around until they were 18 months old.”
Unique was founded in 1984 by Edna Knight after the birth of two of her four daughters with a rare chromosomal disease characterized by a partial duplication of a section of chromosome nine.
Doctors knew of no other recorded cases but, by word of mouth, Ms Knight tracked down four other families whose children had the same anomaly and they formed an ad hoc support group, writing letters to share their experience. .
In 1990 it expanded to include other genetic and chromosomal abnormalities and in 1993 became an official charity.
Advances in genomic sequencing mean that around one in 100 births are now identified as having rare chromosomal disorders, up from one in 200 around 20 years ago.
The technique mirrors that used to track the emergence of new coronavirus variants behind Covid, but instead detaches DNA from children with suspected medical or developmental abnormalities.
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Beverly Searle, CEO of Unique and a former researcher in microbial genetics, first became involved in 1990 after the birth of her daughter Jenny with profound disabilities and medical problems due to a chromosomal abnormality.
She said: “We are very fortunate in the UK to have this fantastic new genomic medicine service now where they can do the most up to date DNA sequencing.
âIt’s incredibly advanced, so they can find the tiniest changes in a single gene – even a single letter change.
âWhen my daughter was born all you could do was look at the stained chromosomes under a microscope, so you had to have really big losses or gains or rearrangements of chromosomal material to detect that there was a problem.
âNow with DNA sequencing at least 40% of those kids are diagnosed and as we refine the technique you will get more and more diagnoses.
“So for many families, we are breaking down this really terrible diagnostic hurdle that many families found themselves on, just trying to find out ‘why is our child like this? Did we do something wrong? â.
“Of course, they didn’t do anything wrong – it’s just that their particular chromosome or genetic disorder couldn’t be detected by technology before.”
To learn more about Unique and its database, visit www.rarechromo.org.