Dermatitis in cats: possible causes of feline miliary dermatitis
Miliary dermatitis: characteristics
Considering the disorders that cause pruritus in cats, we can distinguish four clinical patterns, depending on the affected areas and the severity of the clinical signs. These patterns are:
- Dermatitis on the face and neck
- Miliary dermatitis
- Eosinophilic plaques
- Self-induced symmetrical bilateral alopecia
Miliary dermatitis is a clinical pattern characterised by multiple erythematous papules with brown or black adherent scabs of varying size due to a hypersensitivity reaction. They are typically located in the dorsal lumbosacral region, caudomedial area of the thighs and on the neck,1 although they may follow a generalised manifestation.
Papules are the primary lesion that, by causing pruritus of varying intensity, can progress to secondary lesions, such as alopecia and wounds, due to the animal’s self-induced trauma.
Miliary dermatitis: classification of its causes
Among the underlying causes of feline miliary dermatitis, there is no predisposition for breed, age or sex with regard to the presentation of this skin pattern.
Allergies are considered the primary condition responsible for this clinical picture, although other disorders may be involved. Therefore, it is important to perform a differential diagnosis to find the precipitating factor because if we do not eliminate the source of the problem, the clinical signs will recur.
A leading cause of miliary dermatitis are ectoparasite allergies: fleas, whose bite produces flea allergy dermatitis (FAD), especially in the cat’s lumbosacral region, and mosquitoes, which occur on a seasonal basis in spring and summer. Both types of ectoparasitism have a good prognosis, with treatment based on ovolarvicides and adulticides to eliminate the parasite and the administration of corticosteroids to reduce pruritus.
Dietary allergies are another potential cause of miliary dermatitis in cats and course with highly variable lesions which are easily resolved through balanced diets free from the allergen ingredient. And then there are environmental allergens, either of a seasonal or continual nature.
Miliary dermatitis also develops in cases of generalised infections, either caused by fungi, which give rise to dermatophytosis, or by other pathological agents that trigger superficial pyodermas.
There are various parasitisms that course with feline miliary dermatitis, although in this case it is not due to an allergy to the parasite, but rather the parasite’s direct mechanical action on the cat’s skin. These include the mites that cause different types of mange:
- Notoedric, produced by Notoedres cati, which starts at the tip of the ears.
- Otodectic, also called ear mange, caused by the mite Otodectes cynotis.
- Demodectic, caused by Demodex cati, which does not cause pruritus.
- Cheyletiellosis, triggered by the species Cheyletiella and resulting in a dandruff-like appearance in the animal.
Parasitism by lice can cause pediculosis, which is associated with miliary dermatitis, seborrhoea and alopecia.
It is worth highlighting the autoimmune diseases that can trigger this skin pattern, specifically pemphigus foliaceus . It is usually idiopathic, but can be triggered by certain drugs, such as penicillin. This condition requires treatment based on the administration of immunosuppressants.
Conclusions
While allergies are the main cause that spring to mind, there is a very broad range of diseases that can produce miliary dermatitis in cats. A detailed anamnesis and thorough clinical examination are important to obtain a specific diagnosis so the causal agent can be eliminated.
