General Considerations

1. This section includes (i) canine and feline primary seborrhea, canine acne, (iii) feline acne, (iv) canine ear margin dermatosis, and (v) nasal and digital hyperkeratosis.
2. Primary seborrhea is uncommon in dogs and cats. An underlying disorder is not identified in affected animals, and its pathogenesis is not well known. It has been reported in Persians, Himalayans, and exotic shorthaired cats. Many dog breeds are known to have primary seborrhea. Most dogs will manifest the disease before 2 years of age and cats during the first 6 weeks of life. The hallmark sign is loose or adhered scales of various sizes that can be generalized but typically most noticeable along the dorsum. The excessive scaling can be associated with sebum (i.e. seborrhea oleosa) or not associated with sebum (i.e. seborrhea sicca). Medicated shampoos are an important part of the treatment regimen and the active ingredient selection depends on the type of seborrhea. Agents to restore the damaged skin barrier can be used as adjunctive therapy. The disease is non-curable, thus, treatment is life-long.
3. Some dermatologists believe that canine acne is primarily an inflammatory disease of the facial hair follicle (i.e. folliculitis) that result from trauma and not a keratinization disorder like feline acne. Canine acne is most commonly reported in short coated breeds and develops at a young age. The chin is typically affected but lesions can also develop on the lips and muzzle. Erythematous papules, pustules, and nodules are initially formed at the hair follicle opening. If hair follicles rupture (i.e. furunculosis), lesions will drain and erosions to ulceration may form. Treatment should be based on disease severity and presence of secondary infection.
4. Feline acne is a keratinization disorder of facial hair follicles. A keratosebaceous plug forms inside the hair follicle canal; however, the pathomechanism is not well understood. There is no age, sex, or breed predilection. The chin is always affected but lesions can also develop along the lips. The keratosebaceous material accumulated in the hair follicle canal manifests clinically as comedones (i.e. black heads). Fragments of black keratotic debris also tend to accumulate in the chin area. If the “comedonic” follicles become inflamed due to secondary infection or other causes, erythematous papules and nodules will develop. If affected follicles rupture (i.e. furunculosis), draining tracts will eventually form. Treatment will depend on disease severity and if secondary infection is present. The disease is non-curable, thus, treatment is life-long.
5. Canine ear margin dermatosis is an uncommon keratinization disorder of the skin along the pinna margin. Lesions are typically bilateral. Dachshunds appear to be predisposed but it can occur in other breeds. Keratosebaceous materials are adhered to the skin and hair shafts of pinnae margins. Hairs epilate easily and will eventually lead to alopecia. Fissures can develop in chronic cases. Treatment will depend on disease severity. The disease is non-curable, thus, treatment is life-long.
6. As the name indicates, nasal and digital hyperkeratosis are characterized by the accumulation of adhered keratin on the nasal planum or footpads, or both. The condition typically develops in older dogs. American cocker spaniels and English springer spaniels appear to be predisposed. The excessive accumulation of keratin on the nasal planum and/or footpads can result in the formation of fissures. Typically, all footpads are affected. Severely affected footpads may result in pain and lameness. Treatment will depend on disease severity. The disease is non-curable, thus, treatment is life-long.