• Abstract and Figures
• Public Full-text

Golden Retriever Vol. 10, No. 1 I Fall 2012 Golden Retriever Ichthyosis May Be Underdiagnosed Due to Seborrhea Similarity hen a scaling skin disorder first Ichthyoses are a diverse group of 2 years of age. The age of onset was showed up in Golden Retrievers hereditary, usually congenital, diseases unknown for eight dogs. Win the 1990s, it was frequently characterized by faulty formation of The wide age distribution reflects misdiagnosed as seborrhea, a condition the outer layer of the epidermis, the the subtle nature of the phenotype. 2 that also causes scaling and dandruff. stratum corneum, with resultant The challenge of determining an exact More than a decade later, veterinary scaling. 2,3,4 Skin biopsies have revealed age of onset is difficult as mild scaling specialists began studying the disorder two types of ichthyoses: epidermolytic could have been overlooked. Hereditary and realized it is specific to Golden ichthyosis (EI) and nonepidermolytic ichthyosis is often present at birth, Retrievers. More recently, geneticists ichthyosis (NI). but it is not uncommon for signs to identified the causative mutation Golden Retrievers develop the NI develop later in adulthood. and developed a direct DNA test to type, which also occurs in American “All the dogs had strikingly similar identify affected and carrier dogs. Bulldogs and Jack Russell Terriers though histopathologic changes consisting Fortunately, Golden Retriever in a more serious, yet not common, of mild to moderate hyperkeratosis, ichthyosis is seldom severe. The dis - form. Among the breeds that develop or thickening of the outer layer of skin, order is named for the Greek word EI are Norfolk Terriers, Rhodesian and an absence of epidermal hyper - ichthys, meaning fish, because it looks Ridgebacks and Labrador Retrievers. plasia, which is the proliferation of like fish scales. Breeders sometimes refer A University of Pennsylvania study normal cells, and dermal inflammation,” to the condition as “puppy dandruff” of 46 Golden Retrievers diagnosed Mauldin explains. “Environmental since puppies usually outgrow signs of with ichthyosis from January 2004 to factors including nutrition, supple - flaky skin as they mature, although January 2007 found that all the dogs ments, humidity, estrous cycle, and ichthyosis also occurs in adult dogs. had mild to moderate dry scaling with other skin conditions likely impacted Research in Goldens led to the discovery variable hyperpigmentation on their the degree of scale formation.” that the disorder is similar to one of abdomens. Large, loose scales ranging Electron microscopic analysis of the the human autosomal recessive con - from soft white to gray were described skin of five affected dogs compared genital ichthyoses (ARCI). as looking like snowflakes. with two normal control dogs showed An ongoing survey conducted by the “The dogs looked like walking snow crystalline structures in the outer layer Orthopedic Foundation for Animals in globes,” says Elizabeth Mauldin, D.V.M., of skin, the stratum corneum. Pedigree conjunction with the Golden Retriever associate professor of pathology and analysis of 14 dogs indicated that Club of America (GRCA) reports that dermatology at the University of Golden Retriever ichthyosis is an auto - ichthyosis accounts for 0.2 percent of Pennsylvania School of Veterinary somal recessive condition in which a skin disorders in the breed. “Overall, Medicine. “We documented that the dog inherits a copy of the mutated this is a very low percentage,” says dogs suffered from a primary disorder gene from both its sire and dam. Rhonda Hovan, the GRCA research of cornification, the process of making Not curable, ichthyosis is treated facilitator. “The percentage of affected scale in natural skin turnover. We with moisturizers and emollients to Goldens in this survey probably does determined that a skin biopsy can be provide palliative care. “Corticosteroids, not reflect how many dogs have the used to diagnose the disorder.” such as prednisone, do not improve disease, especially if the diagnosis is The 46 dogs in the study consisted skin condition and actually worsen the based on physical signs alone. It is of 25 females and 21 male Golden skin barrier,” explains Mauldin. “This likely that mild cases go undetected Retrievers. Twenty-two dogs had skin further impairs the body’s natural or ignored. It also is possible that lesions when they were younger than defenses and puts a dog at risk for ichthyosis is inadvertently diagnosed 1 year of age; three dogs developed secondary bacterial and possibly as seborrhea, which accounts for 0.9 the disorder between 1 and 2 years yeast infections.” percent of skin disorders.” of age; and 13 dogs were older than Continued on page 2 An Inherited Congenital Disorder Breeders Can Test Golden Retrievers for Ichthyosis Cindy Williamson of Harford County, Md., who breeds Golden Retrievers under direct DNA test to help identify Golden Retrievers that are carriers, the Lycinan prefix, describes unknow - affected or normal for ichthyosis is available through Antagene, a ingly breeding litters with ichthyosis A since 1992. “It was not diagnosed then diagnostic testing laboratory in La Tour-de-Salvagny, France. Ichthyosis is as ichthyosis,” she says. “The veterinar - a scaling skin disorder with an autosomal recessive inheritance. ian suggested it was ‘walking dandruff,’ The $120 genetic test can be performed from a cheek swab or blood sample. which is caused by mites, but the puppies Samples from Golden Retrievers in the U.S. should be sent to Optigen, a outgrew the condition and quit showing diagnostic testing laboratory in Ithaca, N.Y., which extracts the DNA and ships signs by 8 weeks of age. We called the it to Antagene for DNA testing. Results are available in three to four weeks. puppies ‘peelers’ because of their flaky The GRCA Health & Genetics Committee recommends prebreeding testing skin. We didn’t think much about it primarily for dogs that have clinical signs of ichthyosis and for dogs that because it went away and never per - have close relatives known to be carriers, affected or have clinical signs. sisted into adulthood.” Golden Retriever Ichthyosis ARCI,” says André. “The research trans - of the PNPLA1 gene mutation.” continued from page 1 lated well from Goldens to humans The GRCA Health & Genetics through collaborations with Dr. Judith Committee endorses this approach. Two other studies were simulta - Fisher, a specialist of human ichthyoses It also echoes Casal’s caution regarding neously performed on ichthyosis in from the Institute of Human Genetics unnecessarily reducing the genetic Golden Retrievers. The studies, which at Freiburg University in Germany. diversity that is so vital for long-term took place in England 3 and France, 4 Mutations in the PNPLA1 gene were breed health, Hovan says. concluded similar clinical and histo - identified in two human families Golden Retriever breeder Gayle pathological results. Thus, the three affected by ARCI. This was the first Watkins of Cold Spring, N.Y., who breeds studies led to the hypothesis of an evidence for the involvement of PNPLA1 under the Galyan prefix, concedes autosomal recessive transmission mode. in ichthyosis in dogs and humans.” that she has not been too concerned Random sampling of 500 Golden about ichthyosis since it appears so DNA Discovery Aids Understanding Retrievers in France further supports mildly in most Golden Retrievers. A The discovery of the causative muta - the autosomal recessive inheritance recent litter of seven affected puppies tion for Golden Retriever ichthy osis was and the mutation frequency as follows: made her think twice. made in 2010 by a group of French • Forty percent of dogs are carriers that “We had DNA testing performed geneticists led by Catherine André, inherit one copy of the mutated on the dam when she was pregnant,” Ph.D., head of the Canine Genet ics allele. Though they will not be affected, Watkins says. “Both she and the sire team at CNRS/University of Rennes. they transmit the mutated allele to tested positive. After this happened, The project was funded by CNRS and 50 percent of their offspring. I realized how upset prospective buyers the European Commission under the • Thirty percent are affected, inherit - can become about buying puppies with LUPA initiative that brought together ing two copies of the mutated allele a known flaw.” genomic experts at university and pri - and passing one mutated allele on Two of the puppies had moderate vate laboratories to study the genetics to 100 percent of their offspring. to severe flakes, or dandruff. Scales of dogs and learn more about human Many affected dogs do not show could be seen when the hairs on their diseases. A genomewide associ ation signs of disease, while others coat were parted. “When the puppies study of 40 affected dogs and 40 develop mild to moderate disease. were 19 weeks old, the signs had unrelated healthy ones allowed them • Thirty percent are normal. They disappeared, and eventually, there to identify a genomic region on canine inherit two copies of the normal were no clinical signs,” she says. chromosome 12. allele, and their offspring cannot Once the genetic test was offered, The researchers used candidate gene get the disease even if the other Williamson tested the sire and dam sequencing in 12 affected and 12 healthy parent is affected or a carrier. of a recent litter that produced a Goldens to identify the mutation in the André notes that thus far all affect - puppy with lightly, flaking dandruff. PNPLA1 (patatin-like phospholipase) ed Golden Retrievers have the same Both the sire and dam came back as protein. They found a homozygous mutation. She believes the disease is carriers. “The dam was bred three times insertion-deletion, or indel, mutation less prevalent in Golden Retrievers in before the DNA test was available,” in PNPLA1 that leads to a premature the U.S. compared to those in France she says.

Load more

  4

Copy Link