Lipid Profiles to Diagnose Atopy
Atopic dermatitis, or atopy, is the most common inflammatory skin disease in people and dogs. It is caused by an abnormal immune response to environmental allergens that penetrate the skin’s outer protective layer. Clinical signs include itching, scratching, and licking which predispose the skin to secondary infection. There is no definitive diagnostic test for atopy in dogs. Instead, veterinarians analyze the timing and severity of clinical signs and rule out other causes of itch and skin infection to settle on the diagnosis. Similarly, there are no objective tests to assess the response to treatment, which varies widely. In human medicine, studies suggest that there are different types of atopy with different biochemical mechanisms. The same may be true in dogs.
Fat levels in skin and blood may be helpful to objectively diagnose atopy in dogs.
Scientists do know that atopy is associated with changes in the amounts of various lipids, or fats, in the skin’s epidermal layer. Whether these changes are the cause or result of the abnormal immune response remains unknown. With funding from AKC Canine Health Foundation (CHF) Grant 02651: Discovery of Novel Biomarkers of Canine Atopic Dermatitis through Lipid Profiling, investigators at Purdue University studied these lipid changes in dogs with atopic dermatitis. They collected skin swabs and blood samples from affected dogs before, during, and after treatment with common atopy medications and compared the lipids present with those in samples collected from healthy dogs. Twenty-two dog breeds were studied, and mixed breeds were the most common.
Results of this study indicate that lipid levels (or lipid profiles) may be helpful in objectively diagnosing atopy and assessing the response to treatment.1
The types and relative amounts of various lipids present in the skin was very different between affected and healthy dogs. These changes were evident whether swabs were taken from dog skin that appeared healthy or was affected by a scab, crust, or other lesion. This is exciting news because obtaining a skin swab is a non-invasive, non-painful procedure and results will be helpful when obtained from anywhere on an affected dog’s body.
Lipid changes were also evident in blood samples. This means that atopy is not just limited to a dog’s skin but affects the entire body. Collecting a blood sample is also a relatively non-invasive procedure.
Interestingly, blood and skin lipid changes differed between males and females. However, since most of the dogs studied were spayed or neutered, investigators suspect that something other than sex hormones is responsible for this difference and further study is needed.
Treatment with drugs commonly used to treat canine atopy (Apoquel® and/or Cytopoint®) did alter the lipid levels present in the skin of dogs with atopy. These changes were not consistent though, so additional study is also needed to assess lipid recovery following treatment.
These results are very encouraging, and veterinarians may soon have a non-invasive, more accurate method to diagnose atopy in dogs. In fact, testing for a subset of the lipid changes found in this study could diagnose atopy with 90-95% accuracy. Lipid profiles may also be useful to objectively monitor a dog’s response to treatment. Additional study will examine the sex differences noted in this population, see if lipid changes can be used to predict disease, and explore new treatment targets. Learn more about this work and other CHF-funded studies on atopy at akcchf.org/dermatologyRPA.
- Franco, J., Rajwa, B., Gomes, P., & HogenEsch, H. (2021). Local and Systemic Changes in Lipid Profile as Potential Biomarkers for Canine Atopic Dermatitis. Metabolites, 11(10), 670. https://doi.org/10.3390/metabo11100670
- Exploring Biomarkers for Atopic Dermatitis (04/14/2022)
- Hair Coat Disorder in Schipperkes Resembles Alopecia X (04/01/2019)
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