PKD Life - Spring 2022 - 11

What You Should Know
About Genetic Testing
Insights and advice from nephrologist
Neera Dahl, M.D., Ph.D.
With Debra Gordon
N eera Dahl, M.D., Ph.D., is the director of the
Nephrology Clinical Trials Program at Yale School
of Medicine in New Haven, Connecticut, where she
oversees studies in ADPKD, diabetes, and hypertension.
Her expertise is in the diagnosis and management of
inherited (or genetically based) kidney disease, with a
focus on ADPKD and other cystic kidney diseases that
mimic ADPKD. We talked with her about the role of
genetic testing in people with ADPKD.
patients with ADPKD who
have no known family history.
It's important to make a
genetic diagnosis to ensure
that we're dealing with
ADPKD and not something
that looks like it.
Q How does genetic
testing aff ect
Q Why is genetic testing
important for people
with ADPKD?
ADPKD is a diagnosis made
primarily on clinical grounds.
When we see a patient who
has a family history of the
disease and then look at their
imaging and see cysts in the
kidneys, we typically make the
diagnosis. But it may still be
important to consider genetic
testing because there are
other inherited diseases that
can cause cysts but that have
a very diff erent risk for endstage
kidney disease (ESKD).
For instance, autosomal
dominant polycystic liver
disease (ADPLD) also causes
liver and kidney cysts, but
we think the mutations
that cause ADPKD (but not
ADPLD) are those responsible
for the progression to kidney
failure. So genetic testing
may be important to provide
information about the likely
course of the disease.
Q Are there any other
reasons for doing
genetic testing?
The other times to look at
genetic testing is if someone
in the family had a very different
disease course than
others. For instance, if your
parent was in their 70s when
they developed ESKD, but
you're 30 and already facing
dialysis, then you may benefi
t from genetic testing to
fi nd out what's behind that.
Or if you have liver fi brosis
(scarring) rather than cysts,
that could be related to a
mutation in some other gene
besides PKD1 or PKD2, which
cause ADPKD.
We also recommend testing
for the 10% to 15% of
treatment decisions?
Right now, our treatments are
based on the risk of progression.
Those at highest risk are
the ones treated most aggressively
and who may benefi t
from tolvaptan. However, the
genetic diagnosis can also
be very helpful in assessing
the risk of progression based
on the specifi c mutation and
some clinical features.
Q Are there any
negatives to doing
genetic testing?
Our genetic information
is protected by the Genetic
Information Nondiscrimination
Act. Genetic testing
results cannot be used to
determine medical insurance
costs or availability. However,
the law doesn't protect
against discrimination for
life or disability insurance,
which may require a review of
all your medical information.
Q Is genetic testing
being used to
tailor treatments?
Yes, and that's one of the
really exciting parts of where
the fi eld is going. There are
therapies being developed
that will increase the expression
of polycystin-1 or -2 proteins,
which are defective or
missing in ADPKD. Going forward,
we may be doing genotyping
(genetic testing) to
determine which families will
benefi t from which therapies.
Q Where does
genetic testing come in?
This is something we discuss
with all our young patients,
because if one parent has
ADPKD, they have a 50%
chance of having a child
with the disease. In preimplantation
genetic testing,
in vitro fertilization occurs,
and before the embryo or
embryos are implanted, they
are genetically tested for
evidence of ADPKD. Those
embryos without the genetic
mutation are implanted.
This allows the couple the
opportunity to feel they're
doing everything they can
to prevent the disease in the
next generation.

PKD Life - Spring 2022

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