Rod A.W. Rosychuk, DVM, DACVIM
Colorado State University, Ft. Collins, CO, USA
Atopy and Adverse Food Reactions (AFR; Food Sensitivity)
Both atopy and AFR may be manifest as pruritus and dermatitis targeting only the head and neck area. The most common site for pruritus - induced lesions is the pre-auricular region. Occasionally, a pruritic dermatitis may only be restricted to the chin. Other allergy manifestations that may be restricted to the head include indolent ulcers, eosinophilic granuloma and rarely eosinophilic plaques. Secondary bacterial and Malassezia infections may contribute significantly to pruritus. Skin biopsies usually suggest a hypersensitivity disorder but are not specific (i.e., similar changes with atopy, AFR, FBH, mosquito bite hypersensitivity). Food sensitivities are diagnosed through the feeding of a restrictive diet (home prepared or commercial novel protein or hydrolysate diet) for at trial period of at least 8 weeks. Atopy is largely a diagnosis by rule out. Therapeutic alternatives for atopy are covered elsewhere in these Proceedings.
Eosinophilic Granuloma (EG)
EG may be associated with variable clinical presentations including a swollen chin / lower lip( pink-yellow discoloration of affected skin) or firm, hairless, pink-yellow plaques or nodules on the pinnae or inflammation or papular to nodular lesions occurring at mucocutaneous junctions of the lips or focal areas of alopecia and crusting (variably pruritic) or ulcerative/ proliferative lesions of the tongue, tonsillar region, frenulum or soft palate. EGs are most commonly related to hypersensitivity disorders (FBH, atopy, food sensitivity, mosquito bite hypersensitivity). A heritable form has been described starting between 4 and 18 months of age and often spontaneously resolving by 4 years of age. Diagnosis is by biopsy. Treatment involves diagnosing and controlling the underlying hypersensitivity. While EG manifestations are usually quite glucocorticoid responsive, the oral lesions often require very aggressive therapy (prednisolone, starting at 2 mg/kg/day or oral triamcinolone starting at 0.5–0.7 mg/kg/day or dexamethasone starting at 0.3–0.6 mg/kg/day). Refractory cases may respond to chlorambucil or oral cyclosporine (starting at 5–7.5 mg/kg/day).
Indolent Ulcer (Eosinophilic Ulcer; Rodent Ulcer)
These indurated ulcers of the upper lip are most commonly associated with hypersensitivity (e.g., FBH, atopy, food sensitivity). A heritable tendency has been suggested in some young cats as noted above for eosinophilic granulomas. On occasion, small lesions may be antibiotic responsive. The diagnosis can be supported by biopsy. Small lesions in young cats with no other evidence of allergic skin disease may be treated with benign neglect or trial systemic antibiotic. More advanced lesions are treated with aggressive glucocorticoids (e.g., prednisolone starting at 2 mg/kg/day); refractory cases treated with oral triamcinolone or dexamethasone. Glucocorticoid responsive, but recurrent cases should be worked up and / or treated for FBH, atopy or food sensitivity. Those poorly responsive to glucocorticoids should still have food sensitivity ruled out. Therapy for idiopathic, refractory cases include oral cyclosporine, chlorambucil and glucocorticoid, interferon (120 units / day PO or 1 million units/m2 sub Q three times weekly) or cryosurgery or radiation therapy (variable response).
Drugs (most notably methimazole) may cause an intensely pruritic facial dermatitis which is histologically eosinophilic and must be differentiated from allergy. Therapy: discontinuation of drug.
"Feline acne" is too often used as an 'all inclusive' term to describe a multitude of skin diseases that affect the chin. "Classic" acne involves follicle plugging (comedones) in the chin and lip margin region. Severe accumulation of follicular debris may result in furunculosis and possible secondary bacterial infection. The cause of feline acne is not known. Multiple cats in the same environment have been noted to develop feline acne at the same time, suggesting a possible underlying viral 'trigger'. Important other diseases that may target the chin, producing diffuse inflammation and variable amounts of crusting include bacterial dermatitis, Malassezia dermatitis (usually secondary to allergies), atopy, food sensitivity, dermatophytosis, eosinophilic granuloma, demodicosis, discoid lupus erythematosus pemphigus foliaceus and contact hypersensitivity (i.e., food bowl). Although these diseases are unassociated with comedo formation, 'true' acne lesions can be exacerbated by 'flares' of other diseases that target the area, such as allergy. Treatments for 'uncomplicated' feline acne include topical mupirocin (BID) or either Douxo Seborrhea Spot-on or Douxo Calm Gel (daily or every other day). Alternatives include topical 1% clindamycin, 2% erythromycin or metronidazole gel. The area can be periodically cleaned with a sulfur/salicylic acid shampoo. For severe disease (secondary infection, furunculosis), consider sedation/anesthesia to express comedones and cysts (ideal to lance prior to expressing) followed by a systemic antibiotic and systemic glucocorticoid or topical steroid (e.g., Synotic - fluocinolone, DMSO). Multiple cat outbreaks often spontaneously resolve in 3–5 months. Therapy for a possible viral component include L-lysine (250 mg BID), famciclovir (125 mg BID) and oral interferon (120 U PO daily).
Herpesvirus 1 Associated Dermatitis and Stomatitis
Facial dermatitis and stomatitis has been associated with Herpesvirus 1. Affected cats often have histories of recurrent or persistent mild upper respiratory tract infection, recent stress or the administration of glucocorticoids, suggesting exacerbation of a latent viral infection. Lesions are usually focal and located most commonly on the dorsal and lateral muzzle and the periorbital regions. The planum nasale may be affected. Lesions are characterized by focal erosion, ulceration, erythema, swelling, and exudation of variable degrees and may be painful and variably pruritic (can be very pruritic). A concurrent stomatitis is only occasionally noted. Histologically, inclusions may be seen in more acute lesions. Eosinophils are often seen in large numbers, potentially resulting in a miss-diagnosis of allergic dermatitis or mosquito bite hypersensitivity. Alternative diagnostics include immunohistochemistry for feline herpesvirus or PCR (the latter being superior). Lesions usually do not respond to glucocorticoids. The treatment of choice at this time is Famciclovir (Famvir, Novartis; 125 mg TID–BID). Secondary bacterial infections should be treated with amoxicillin- clavulanate, doxycycline, clindamycin or cefovecin. Alternative therapies include L-lysine, 250 mg (1/2 tab) BID , Alpha interferon, 1.0–1.5 million units / m2 SubQ three times weekly for 4–8 weeks or 3,000 IU PO q 24 hrs or Imiquimod (Aldara, 3M) topically three times weekly.
Idiopathic Facial Dermatitis of Persian and Himalayan Cats
Age of onset is 4 months to 5 years (median 12 months). There appears to be a heritable tendency. The first abnormality noted is an accumulation of black debris in the periocular, perioral and/or chin areas. Although not pruritic initially, pruritus does develop during the course of the disease and may become moderate to severe. Affected skin becomes progressively inflamed. A bilateral erythematous otitis externa with accumulation of black waxy material within the ear canals is common. Secondary Malassezia and bacterial infections are common and important contributors to the symptomatology. Skin biopsies are supportive. Response to glucocorticoids is variable and often poor. More recently, this disease has shown variable response to oral cyclosporine (5–7.5 mg/kg/day).
Bowenoid In situ Carcinoma (Bowen's Disease)
Bowen's disease is usually noted in older cats (e.g., > 10 years)and is manifest as singular to multifocal, heavily crusted plaques and 'wart-like' lesions that often target pigmented or non pigmented areas of the head. Many cases are noted to have papillomavirus in affected areas suggesting that this may be the initiating cause of the lesions. ¼ of reported cases are noted to be positive for FIV or FeLV. Demodex may be found in the follicles of affected (Bowenoid) areas. Squamous cell carcinoma has been noted to develop in about 20% of cases; basal cell carcinomas may also arise from the lesions. Diagnosis is by biopsy. Therapy for asymptomatic lesions may not be necessary. 90Strontium plesiotherapy (B-irradiation) has been effective in healing thin (less than 2–4 mm) lesions. CO2 laser therapy can be effective although it may not be curative. Oral acitretin (a Vitamin A analog; 3 mg/kg/day) may be effective. Imiquimod (topical immune response modifier; Aldara, 3M Pharmaceuticals) is the author's current treatment of choice. It is applied three times weekly. It is common to see irritation (erythema, edema, crusting, erosion) at sites of application. If significant irritation noted, the frequency of administration is decreased.
Infection with the Cryptococcus neoformans - C. gattii complex begins in the nasal cavity. Destruction of facial bones may result in spread of the infection to the bridge and sides of the nose (firm or fluctuant subcutaneous swelling), planum or hard palate. Proliferative lesions may be seen in the nares. There may be sneezing, epistaxis and discharge. Infection may be disseminated from here to the CNS and other areas of the body. Diagnosis is based on cytology of swabs, impression smears, or tissue aspirates, culture and/or histology or a latex agglutination antigen test. Therapy: ketoconazole (for cryptococcosis diagnosed in the US Pacific Northwest), itraconazole (5–10 mg/kg BID), fluconazole (30–50 mg/day; for cryptococcosis diagnosed in Australia) or amphotericin B (especially if CNS involvement).