Flawed gene passed down through the generations

Researchers have identified a novel genetic disorder that affects a small number of Quebec families

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Sheryl Ubelacker, THE CANADIAN PRESS TORONTO — Researchers have identified a novel genetic disorder that
affects a small number of Quebec families and pinpointed the mutated gene
that can cause the disabling disease in their children.
Dubbed MEDNIK after its collection of varied symptoms, the genetic disease
has been found so far in five families in the province, with eight of their
members affected.
“Many of the patients died before the age of two,” said Dr. Patrick
Cossette, a neurologist and geneticist at the University of Montreal. “We
still have some patients that are alive and they can live beyond 10 years
old, but they are severely impaired.”
Cossette, principal investigator of the research group that named the
condition and isolated its genetic underpinnings, said MEDNIK is extremely
rare. It has been traced back through genealogical records to a French
colonist who settled in eastern Quebec in the 1600s.
The disorder is considered one of the founder-effect genetic diseases, so
called because they have been passed down through the generations from
founding populations in a specific geographic area.
MEDNIK is an acronym of the symptoms: mental retardation; enteropathy
(poor food absorption); deafness; peripheral neuropathy (a problem with
nerve and muscle connections); ichthyosis (dry scaly skin); and
keratodermia (horn-like skin growths).
“They have severe developmental delay,” Cossette said of children born
with the syndrome. “They have severe feeding problems because of bad
absorption of the food and they have severe skin lesions. And on top of it
they are deaf.”
“They cannot walk, for example, because they are too weak. And they have
bad muscular tone, so they are not strong enough to walk.”
At first, the researchers thought the disease afflicting some members of
the families was an atypical form of keratodermia. But when they submitted
their study for publication to the Public Library of Science, the journal
editor and experts reviewing the paper decided that what the researchers
were describing was a “distinct entity.”
The study is published in this week’s edition of PLoS Genetics.
“So we found the specific gene for this entity, but eventually this can
have implications not only for the families in Quebec, but maybe the
disease will be recognized elsewhere in the world and maybe even more
easily recognized in the province of Quebec, as well,” said Cossette.
“There are probably many cases that aren’t being diagnosed as such.”
Julie Leclerc-Michaud of Saint-Jerome, Que., just north of Montreal, has
three children. Her eldest, Etienne, was born with MEDNIK and is mentally
and physically disabled.
Etienne, 14, is deaf, cannot walk, is incontinent and has extensive skin
problems. He is unable to eat many foods because of poor digestion and has
significant developmental problems, she said in a phone interview.
“His mental age is approximately one, two years of age. He’s severely
Cossette said both parents must carry the genetic mutation for the
syndrome to occur in their offspring. There is a one in four chance that a
child will get copies of the gene from both parents and be born with the
While there is no treatment for the condition, isolation of the flawed
gene means doctors will be able to test family members to see if they are
carriers and to provide prenatal testing to determine if a fetus is
Leclerc-Michaud said that even though the discovery will not provide any
remedy for their son and others with the disease, it means her younger son
and daughter, as well as nieces and nephews, will be able to make
family-planning decisions based on genetic testing.
That was not an option available to Leclerc-Michaud, who recalled the fear
she felt while pregnant that her other babies could be born with the same
condition that afflicted her first child.
“They will know what to expect if they ever become pregnant ... or if they
want to have children,” she said of the younger generation. “That’s a big
plus already, not to play roulette with their future and a child who would
be very ill."
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