Seborrhea

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Seborrhea sicca on the skin of a dog[1]

Seborrhea (canine seborrheic dermatitis) is a skin disease characterized by excessive flaky skin (dandruff) and greasiness caused by alterations in skin surface lipids[2].

This condition may be either a congenital disease or acquired as a result of an underlying secondary disease[3].

Primary seborrhea is an inherited disorder of keratinization or cornification more commonly seen in the American Cocker Spaniel, English Springer Spaniel, West Highland White Terrier, Shih Tzu and Basset Hound. It is characterized by hyperkeratotic scaling, greasy pruritic dermatitis with adherent crusts developing over the ventral trunk, ears, genitals, claws or foot pads. Associated erythema, lichenification, hyperpigmentation and excoriations are usually evident on visual examination[4].

With primary seborrhea, lesions usually start to develop between 12 - 18 months of age and are progressively worsen over time. Secondary overgrowth with yeast (Malassezia spp[5] and Candida spp[6]) and bacteria (Staphylococcus pseudintermedius) is common.

As a result of secondary bacterial and yeast overgrowth, a characteristically offensive cheesy odor may manifest and other diseases may ensue, such as alopecia, folliculitis, intertrigo, impetigo, paronychia and pyoderma[7].

A diagnosis is usually acquired by clinical history and findings, as well as supportive skin biopsy, skin cultures and histological examination of skin biopsies.

Histologically, two basic forms are recognized - oily seborrhea (seborrhea oleosa) and dry seborrhea (seborrhea sicca). Most dogs are affected by both.

Secondary causes of seborrhea which need to be distinguished from primary seborrhea would include sebaceous adenitis, atopy[8], hypothyroidism[9], hyperadrenocorticism[10], hyperestrogenism, Demodex spp, food allergy, nasal parakeratosis, zinc-responsive dermatosis, Leishmania spp[11], psoriasiform-lichenoid dermatosis, drug eruptions and lupus erythematosus. Treatment of secondary causes is essential to resolve the skin disorder.

Treatment is usually successful with long-term topical keratolytic shampoos[12] and topical humectants. bacterial overgrowth syndrome usually requires an extended course of cephalexin at 30 mg/kg/day.

Oral fatty acid supplementation is often recommended, such as retinoic acids (e.g etritinate 1mg/kg daily for 2 - 3 months) and may assist resolution of lesions[13].

References

  1. Web MD
  2. Yoon JS et al (2013) Skin lipid profiling in normal and seborrhoeic shih tzu dogs. Vet Dermatol 24(1):84
  3. Hernblad Tevell E et al (2008) Sebaceous adenitis in Swedish dogs, a retrospective study of 104 cases. Acta Vet Scand 50:11
  4. Pin D et al (2006) Prospective study of bacterial overgrowth syndrome in eight dogs. Vet Rec 158(13):437-441
  5. Maynard L et al (2011) Comparison of two shampoos for the treatment of canine Malassezia dermatitis: a randomised controlled trial. J Small Anim Pract 52(11):566-572
  6. Yurayart C et al (2011) Comparative analysis of the frequency, distribution and population sizes of yeasts associated with canine seborrheic dermatitis and healthy skin. Vet Microbiol 148(2-4):356-362
  7. DCAVM.org
  8. Nagle TM et al (2001) A randomized, double-blind, placebo-controlled trial to investigate the efficacy and safety of a Chinese herbal product (P07P) for the treatment of canine atopic dermatitis. Vet Dermatol 12(5):265-274
  9. Shiel RE et al (2007) Tertiary hypothyroidism in a dog. Ir Vet J 60(2):88-93
  10. Frank LA (2006) Comparative dermatology - canine endocrine dermatoses. Clin Dermatol 24(4):317-325
  11. Cavalcanti A et al (2012) Canine cutaneous leishmaniasis caused by neotropical Leishmania infantum despite of systemic disease: A case report. Parasitol Int 61(4):738-740
  12. Viaud S et al (2012) Comparison of two shampoos as sole treatment for canine bacterial overgrowth syndrome. Vet Rec 170(26):675
  13. Rosser EJ (2000) Therapy for Sebaceous Adenitis. In: Bonagura JD, Kirk RW, editor. Kirk's Current Veterinary Therapy XIII. Philadelphia: WB Saunders Co. pp:572–573