For autosomal recessive disorders, dogs with two copies of the variant are at risk of developing the condition. Dogs with one copy of the variant are considered carriers and are usually not at risk of developing the disorder. However, carriers of some complex variants grouped in this category may be associated with a low risk of developing the disorder. Individuals with one or two copies may pass the disorder-associated variant to their puppies if bred.
At risk dogs are highly likely to show signs of this disease in their lifetime.
Partner with your veterinarian to make a plan regarding your dog’s well-being, including any insights provided through genetic testing. If your pet is at risk or is showing signs of this disorder, then the first step is to speak with your veterinarian.
Ichthyosis, sometimes called “fish-scale disease”, is a type of cornification disorder in which the outer layer of skin does not develop properly, resulting in chronic scaling. Ichthyosis Type 2 (ICH2) is clinically similar to Ichthyosis Type 1 (ICH1), with affected dogs having large, loose, white to gray colored, greasy scaling of the skin that is mostly localized to the body’s trunk. Scaling does not typically show on the head and extremities, although thick white scaling may be present on the inner pinnae (ear flap). Powdery skin flakes, similar to dandruff, may also be present within the coat. The scales may blacken over time, and sparsely haired areas like the belly and axillary regions may develop hyperpigmentation (darkening in color). Rarely, otitis and paw pad thickening can develop. Age of onset is generally early with many affected dogs developing signs by a few weeks of age. Although, there are some affected dogs where signs may not be readily apparent until adulthood. It is proposed this may be because the disorder is generally mild to moderate in nature for those individuals. However, some affected dogs can experience more severe signs leading to skin infections which cause itching and discomfort. Microscopically, ICH2 reveals a thicker outer layer of skin which may indicate a more severe skin barrier defect than ICH1. Breeders experienced in ICH have also noted a more severe and adherent scaling with ICH2. At present, ICH2 appears to be limited to dogs from North America.
There is no cure for Ichthyosis Type 2, but there are measures that can help manage the disorder. Specific treatment plans will vary depending on the severity of an individual dog's clinical signs. Treatments primarily rely on increased hygiene measures such as frequent brushing, regular bathing with kerato-regulating shampoos and rinses, and usage of emollients and moisturizing sprays. A fatty acid-enriched diet or supplements should also be considered to help improve skin and coat health. If secondary bacterial or fungal skin infections develop, appropriate oral and/or topical treatments will be required. In difficult to manage cases, treatment with a synthetic retinoid could be considered. However, a benefit-risk analysis should be conducted prior to initiating long-term treatment with oral retinoids as the side effects of long-term usage have not been fully investigated and additional monitoring is advised while undergoing treatment.
There are many responsibilities to consider when breeding dogs. Regardless of test results it is important that your dog is in good general health and that you are in a position to care for the puppies if new responsible owners are not found. For first time or novice breeders, advice can be found at most kennel club websites.
This disorder is autosomal recessive, meaning two copies of the variant are needed for a dog to be at an elevated risk for being diagnosed with the condition. A carrier dog with one copy of the Ichthyosis Type 2 (ICH2), (Discovered in the Golden Retriever) variant can be safely bred with a clear dog with no copies of the ICH2 (Discovered in the Golden Retriever) variant. About half of the puppies will have one copy (carriers) and half will have no copies of the variant. Furthermore, a dog with two copies of the ICH2 (Discovered in the Golden Retriever) variant can be safely bred with a clear dog. The resulting puppies will all be carriers. Puppies in a litter which is expected to contain carriers should be tested prior to breeding. Carrier to carrier matings are not advised as the resulting litter may contain affected puppies. However, in order to further reduce the prevalence of this variant in the breed population, use of dogs with one or two copies of the variant should be critically considered prior to matings. Please note: It is possible that disorder signs similar to the ones associated with this ICH2 variant could develop due to a different genetic or clinical cause.
All coordinates reference CanFam3.1
Kiener, S., Wiener, D.J., Hopke, K., Diesel, A.B., Jagannathan, V., Mauldin, E.A., … Leeb, T. (2022). ABHD5 frameshift deletion in Golden Retrievers with ichthyosis. G3 (Bethesda), 12(2), jkab397. View the article