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| − | ==Introduction==
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| − | Seborrhea is characterised by a '''defect in keratinisation or cornification'''. This results in increased scale formation, a greasy skin and hair coat and often secondary inflammation and infection.
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| − | There are large amounts of free fatty acids and cholesterol and decreased amounts of diester waxes in surface lipids which lead bacterial populations to become pathogenic [[:Category:Staphylococcus species|coagulase positive staphylococci]].
| + | *Epidermal growth or differentiation disorder |
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| − | It is a '''chronic disease''' affecting mainly dogs, but also sometimes cats and horses.
| + | ===Seborrheic disease complex=== |
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| − | ==Primary Idiopathic Seborrhea==
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| − | This is a common '''inherited skin disorder''' seen most frequently in '''Cocker Spaniels'''. Basal epidermal cells in affected dogs undergo accelerated cellular proliferation and turnover.
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| − | There is an increase in the number of actively dividing basal cells, a '''shortened cell cycle''', and a decreased transit time to the stratum corneum (7-8 days compared with 21-23 days). Hair follicles and sebaceous glands are also affected.
| + | *Abnormal cornification or function of sebaceous glands |
| | + | *Large amounts of free fatty acids and cholesterol |
| | + | *Decreased amounts of diester waxes in surface lipids |
| | + | *Bacterial population changes to pathogenic [[:Category:Staphylococcus species|coagulase positive staphylococci]] |
| | + | *Chronic disease affecting mainly dogs, sometimes cats and horses |
| | + | *Dry form - white to grey scales |
| | + | *Greasy form - scaly, excess brown to yellow lipids sticking to skin and hair |
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| − | Abnormal keratinisation begins from a '''very early age''' and tend to worsen with time. | + | ===Primary idiopathic seborrhea=== |
| | + | *Abnormal cornification |
| | + | *Epidermal turnover reduced to about 2/3 of normal |
| | + | *Microscopically: |
| | + | **Hyperkeratosis distending follicular ostia causing papillary appearance |
| | + | **Parakeratosis at edges of follicular ostia |
| | + | **Congested, oedematous dermal papillae |
| | + | **Spongiotic epidermis with leukocytes |
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| − | ==Secondary Seborrhea== | + | ===Secondary seborrhea=== |
| − | Secondary seborrhea occurs due to an '''underlying disease''' predisposing to excessive scale, crusting and oiliness.
| + | *Develops secondarily to many types of disease (''e.g.'' [[:Category:Integumentary System - Parasitic Infections|ectoparasites]], [[:Category:Integumentary System - Mycotic Infections|fungal infections]], [[Endocrine effects on the skin - Pathology|endocrine disease]], internal disease or allergy) |
| | + | *Microscopically: |
| | + | **Hyperkeratosis and/or parakeratosis of follicles and epidermis |
| | + | **Lesions relevant to the other disease |
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| − | The most common causes are endocrinopathies and allergies, but other diagnoses should be considered.
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| − | For animals '''under the age of one''': [[demodecosis]], [[cheyletiellosis]], [[scabies]], nutritional deficiencies, icthyosis, epidermal dysplasia, food hypersensitivity and [[Atopic Dermatitis|atopy]].
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| − | In animals up to five years old, '''allergy''' is the most common cause of seborrhea.
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| − | In animals over the age of 5 an '''endocrinopathy''' or neoplasia become more likely.
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| − | ==Clinical Signs==
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| − | Clinical signs are very similar between primary and secondary seborrhea cases.
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| − | Mild forms of seborrhea show: '''greasy scales''' around the nipples, lips folds and external ear canal.
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| − | More severe forms show: more severe and generalised lesions, with multiple coalescent scaly or crusty pruritic patches, digital hyperkeratosis and dry, brittle claws. '''Otitis''' can be a prominent feature in some cases.
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| − | The degree of pruritus is useful in ruling out certain diseases.
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| − | If the '''pruritus''' is minimal, endocrinopathies, neoplasia and demodecosis should be considered, and allergies and scabies become less likely.
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| − | Seborrheic dogs are prone to developing '''secondary infections''' with bacteria and ''Malassezia'' and this can have a marked effect on pruritus, which can become severe.
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| − | Other '''systemic signs''' may be present if a systemic disease is causing the seborrhea, such as polyuria/polydipsia, abnormal oestrous cycles, the influence of diet, the environment or the season.
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| − | ===Diagnosis===
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| − | The diagnosis of primary seborrhea is made '''by exclusion'''.
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| − | A thorough physical and dermatological examination is made to attempt to identify an underlying cause.
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| − | '''Cytology''' should be performed on the affected area to determine the bacterial and fungal load. This will help determine the best treatment.
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| − | Other tests include: '''deep skin scrapings, fungal culture, impression smears and coat brushings'''.
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| − | '''Haematology, biochemistry and urinalysis''' may be helpful in identifying any systemic problems.
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| − | '''Biopsies''' are recommended, and for primary seborrhea, will show a hyperplastic superficial perivascular dermatitis. There is usually orthokeratotic or parakeratotic hyperkeratosis, follicular keratosis and apoptosis of keratinocytes.
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| − | There may be inflammation, and parakeratotic caps overlie oedematous dermal papillae.
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| − | Bacteria and yeast are numerous at the surface and evidence of secondary bacterial infection is common.
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| − | ===Treatment===
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| − | Primary seborrhea cannot be cured, but it can be managed in most dogs.
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| − | In dogs with secondary seborrhea, the effort should be placed on curing or managing the underlying disease.
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| − | In all cases, '''antibiotics or an antifungal''' may be necessary at first to cure secondary infections. Cytology can be performed during treatment to check for any recurrence of infection.
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| − | Shampoos can also be used to decrease the bacterial load, aid pruritus and normalise the epidermal turnover rate.
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| − | The mainstay of therapy is the use of '''antiseborrheic shampoos and moisturisers''':
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| − | :'''Keratinolytic''' products: salicylic acid, tar, selenium sulfide, propylene glycol, fatty acids, and benzoyl peroxide. These lead to sloughing of surface keratinocytes and reduce the scale.
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| − | :'''Keratinoplastic''' products: tar, sulfur, salicylic acid, and selenium sulfide. These slow down epidermal basal cell mitosis.
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| − | :'''Emollients''': lactic acid, sodium lactate, lanolin and oils. These reduce water loss from the skin and maintain hydration.
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| − | :'''Antibacterial''' agents: benzoyl peroxide, chlorhexidine, iodine, ethyl lactate.
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| − | :'''Antifungal''' agents: chlorhexidine, sulfur, iodine, ketoconazole, and miconazole
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| − | Shampoos usually combine different agents, and the selection should be made on the basis of the scaliness and oiliness of the coat.
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| − | Cleansing and emollient agents are usually sufficient in mild cases.
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| − | Sulfur, salicylic acid and benzoxyl peroxide should be used in more severe cases needing agents with keratinolytic, keratinoplastic and antimicrobial effects.
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| − | In most cases the '''prognosis is good''', but treatment is usually complex and involves a lot of input from both the vet and the owner.
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| − | {{Learning
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| − | |flashcards = [[Small Animal Dermatology Q&A 19]]
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| − | ==References==
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| − | Harvey, R. (2009) '''A colour handbook of skin diseases of the dog and cat''' ''Manson Publishing''
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| − | Muller, G. (2001) '''Small Animal Dermatology''' ''Elsevier Health Sciences''
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| − | Merck and Co (2008) '''The Merck Veterinary Manual''' ''Merial''
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| − | {{review}}
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| − | {{OpenPages}}
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| − | [[Category:Dermatological Diseases - Dog]][[Category:Dermatological Diseases - Cat]][[Category:Dermatological Diseases - Horse]]
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| − | [[Category:Expert Review]]
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| | [[Category:Integumentary System - Pathology]] | | [[Category:Integumentary System - Pathology]] |