From a retrospective study conducted at the University of Vienna the first confirmations of an association that had already emerged in humans.
In dogs, atopic dermatitis is a chronic dermatologic disease of an inflammatory nature characterized by intense itching, which has many similarities to the form affecting humans. In both cases, the pathogenesis is multifactorial and involves genetics, environmental exposure and IgE-mediated sensitization to environmental and food allergens. A key factor is the inflammatory component, which results in a systemic response that affects not only the skin but involves several organs and systems. In humans, several studies have shown that atopic dermatitis is associated with comorbidities such as asthma and allergic rhinoconjunctivitis, cutaneous and extracutaneous infections, psycho-behavioral manifestations, and the risk of seizure-like manifestations.
In dogs, apart from the increased risk for the animal with atopy to develop epitheliotrophic lymphoma, data on the comorbidities of atopic dermatitis are lacking. Recently, a study conducted at the University of Vienna and published in Veterinary Dermatology investigated in a small group of dogs the hypothesis that-as is the case in humans-the risk of seizures and epilepsy also increases in dogs with atopic dermatitis.
Eloquent results
The Austrian investigation-a retrospective case-control study-involved 34 dogs with atopic dermatitis and 34 nonatopic controls, overlapping in breed and age. Owners were surveyed through a special questionnaire, investigating the presence or absence of signs of seizure activity and other possible comorbidities.
The results are eloquent:
- Seven of the 34 dogs with atopic dermatitis (21%) also had seizure activity, while among the 34 nonatopic dogs only one with seizures (3%) was identified.
- Statistically, atopic dermatitis was significantly associated with a higher frequency of seizure activity (P = 0.035), and dogs with atopy were seven times more likely to develop seizures (OR 95% CI) than controls. No other comorbidities emerged.
- The mean age of dogs with atopy and seizure symptoms was 8.9 years. Based on the owners’ statements, six presented generalized seizures and two presented focal seizures. The diagnosis had been made by the veterinarian of a primary care center, and seven out of eight dogs were being treated with anti-epileptic drugs.
The role of inflammation
Analyzing the mechanisms believed to underlie seizures in an atopic subject, the authors point out that an important role would fall to a systemic inflammatory process, with the involvement of cytokines and mast cells with pro-inflammatory activity that come into play in both atopic dermatitis and epilepsy.
In practice, after an initial acute reaction, especially in the presence of concomitant bacterial infections, the subject with atopy develops a predominant chronic Th1-type response and a marked systemic inflammation that can result in a neuroinflammatory process, inducing a state of hyperexcitability and the appearance of seizures.
It is likely that inflammation represents only part of the multifactorial pathogenesis of atopic dermatitis and epilepsy and the complex correlation linking the two diseases.
Meanwhile, the Austrian study highlighted the increased risk of seizures that accompanies atopy in dogs, just as it does in humans. The fact that this is a retrospective analysis and that it involved a small number of cases can be seen as a limitation of the work, but it has the merit of having paved the way for larger prospective studies confirming these early findings.
Reference
Herrmann I, Kradischnig C, Skor O, Pakozdy A, Panakova L. Higher prevalence of seizure activity in a small population of atopic dogs: a retrospective breed- and age-matched study. Vet Dermatol. 2020;10.1111/vde.12913.
