Feline acne is a relatively common skin disease of the chin gland of cats.
Acne is categorized as a superficial pyoderma. Unproven causal factors include changes in hair growth cycle, poor grooming habits, hormonal changes, secondary folliculitis by Malassezia spp and Pasteurella multocida, excessive sebum production by chin glands, viral infections (e.g. FHV, FeLV, FIV) and contact allergy to food bowls, floor and wall surfaces, etc. In contrast to humans, acne in cats is not confined to adolescence.
The primary change in feline acne is presumed to be an alteration in normal keratinisation in the hair follicle. Initially, keratinous material accumulates in the lower follicular infundibulum resulting in comedo (blackhead) formation. As keratinous material accumulates, it squirts out the follicular ostia, resulting in follicular casts. One theory proposes that affected cats may have larger sebaceous glands in the chin resulting in excessive or abnormal sebum production. In humans, linoleic acid concentration is lower in the sebum of people with acne and anecdotal reports exist of responses to n-6 fatty acid supplementation in cats with feline acne.
No bred predilections have been noted, but there may be a gender predilection for neutered males.
Multiple cases of feline acne have been observed in catteries and multi-cat households and an infectious aetiology has been incriminated but never confirmed. In some of these cases, an upper respiratory virus has been a concurrent problem and immunosuppression, direct viral influence and stress have been proposed as contributing factors. In one recent study, seven of 22 cats with feline acne demonstrated concurrent clinical signs consistent with URTI (Guaguere & Prelaud, 2000). While no evidence of FHV-1 was found histopathologically or immunohistochemically in any cat, in one affected cat from a household with five cats simultaneously having feline acne, feline caliciviral (FCV) antigen was detected in the biopsy of the chin by immunohistochemistry. Chin samples from all other affected cats, as well as the five healthy control cats were negative for FCV. This suggests that FHV and FCV are probably not important in cats with chronic acne.
More advanced cases of feline acne with secondary folliculitis and furunculosis are often complicated with secondary bacterial infection but bacterial infection is not causal. Three types of bacteria have been previously reported to be involved in feline acne: Pasteurella multocida, beta-haemolytic streptococci, and coagulase-positive Staphylococci. Yeast, such as Malassezia spp and Candida organisms, are occasionally isolated. There is no evidence to support that androgenic hormones play a role in feline acne.
Diagnosis of acne in cats is based on obvious signs of chin comedones, with scattered areas of dark crusts or keratinous debris and mild alopecia of the region. Other cats develop erythema, papules, pustules, variable swelling, and pruritus of the lower jaw and chin, In more severe cases, painful form nodules develop, with diffuse oedema and fistulation, leading to scarring. Regional lymphadenopathy may also be present.
Microbial culture often reveals coagulase-positive Staphylococcus spp and alpha-hemolytic Streptococcus spp infection. Other organisms less commonly involved include Pasteurella spp and beta-hemolytic streptococcus. In humans, Proprionibacterium acnes is the principal organism involved with inflammatory acne lesions.
Although the diagnosis of chin acne is relatively easy, identification of the underlying trigger can be more challenging. Often chin acne is a clinical sign of a whole-body skin disease. Some cats with underlying allergic skin disease (atopy, food hypersensitivity) will have chin and perioral region involved as part of their pruritic distribution.
Treatment of feline acne depends on the severity of the condition. Removing excess sebum is the aim. Some treatments include topical cleaning with an antibiotic soap, hydrogen peroxide, iodine (Betadine) or Epsom salts. Topical Vitamin A may assist healing; topical retinoids such as 0.05% Isotretinoin ointment q 24hrs for 4 weeks and then every 48 hours to twice a week. In more severe cases, cleansing the skin with an ointment or gel containing benzoyl peroxide (such as OxyDex) or chlorhexidine may be of use.
Some cats who exhibit severe oedema and furunculosis may benefit from a 10 day course of prednisolone. Topical glucocorticoids can be used to reduce inflammation, such as 1-2 mg/kg prednisolone orally every 24 hours. This treatment may reduce scar tissue formation. Bacterial and fungal infections should be ruled out prior to administering corticosteroids.
Fatty acid supplementation, such as evening primrose oil have been shown to improve clinical signs, given at doses of 1g/5kg bodyweight daily. Fatty acids can reduce inflammation and normalise keratinisation.
Broad-spectrum antibiotics are the mainstay of treatment. Combinations of antimicrobials include:
Systemic antifungals have been trialled in refractory cases and include:
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