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For
generations Lhasa Apsos and Shih Tzu have fallen victim to a serial killer
- hereditary kidney dysfunction. More than 50 years ago, the late Marie
Stillman (Americal's Lhasas) referred to it as 'this miserable thing." Now
we finally may have the key to eradicating this killer from our two
breeds.
Hereditary
kidney hypoplasia (HKH) - also known as hereditary kidney dysfunction (HKD)
and hereditary renal dysfunction (HRD) - has for years afflicted most
established lines of Lhasa Apsos and Shih Tzu. Unlike kidney failure, in
which normal kidneys succumb to disease, HKH is characterized by failure
of the juvenile kidney cells to mature normally (at age 8 - 10 weeks).
Hypoplastic kidneys never fully function. The best advice that could be
offered was that afflicted dogs and their offspring not be bred.
Early
cases of KHK were misdiagnosed as diabetes insipidus because the excessive
thirst of afflicted puppies mimics that disease. Besides excessive thirst,
symptoms of HKH include frequent urinations, dilute urine, protein in the
urine, lethargy, and vomiting. The most challenging aspect of HKH
diagnosis is determining the degree of affliction, which ranges from
severe to very mild without symptoms. Standard urinalysis tests are of
limited value because abnormal results are obtained only when kidney
function is 25 percent of normal or less. To date, the only test capable
of identifying the presence of HKH in all degrees has been a surgical
wide-wedge kidney biopsy. But the biopsy does not identify dogs with
normal kidneys who are genetic carriers. It's been hoped that carriers
could be identified by breeding results.
For
decades breeders pursued veterinary research and spent large sums of money
vainly seeking noninvasive and reliable tools for definitive diagnosis of
HKH. Meanwhile, a very determined Lhasa fancier whose dogs were struck
with HKH fought back. Debby Rothman, of Colorado, embarked on a mission to
create a database of afflicted and clear dogs from within her own lines.
Each dog was surgically biopsied, revealing some previously unrecognized
mild cases of HKH. Pedigrees, lab results, and breeding records were
crossmatched.
Two years
ago the American Lhasa Apso Health trust and the American Shih Tzu Club
jointly funded research in HKH by Dr. Mary Whiteley. As the foundation of
her work, Dr. Whitely relied on the information Rothman has amassed.
Working feverishly, Dr. Whitely discovered first one genetic mutation,
then a second, that she is confident are markers for the disease. (The
second mutation was a surprise, and is found only in puppies who die of
HKH prior to 12 weeks of age.)
Dr.
Whitely has said that sequencing the genes for HKH was particularly
challenging and frustrating. Without access to the pedigrees and screening
compiled by Rothman, she would not have been able to make the progress she
did. The cooperation of many other breeders who have donated cheek-swab
DNA samples and pedigrees of Lhasas and Shih Tzu who are afflicted with
HKH, or have produced or are relation to afflicted dogs, has been
invaluable in validating the research results.
We are
optimistic that soon we will have a simple DNA marker test for afflicted
and carrier dogs. The rest will be up to breeders. As Marie Stillman wrote
when she chronicled the history of her breeding experience with this
miserable thing, "Only fools give advice, and wise men take it."
AKC Gazette, June 2006, pg 66
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