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Mucocutaneous pyoderma

01 July 2014, at 1:00am

David Grant continues the series of dermatology briefs

Mucocutaneous pyoderma is a rare disease seen in dogs. It affects the lips and peri-oral skin mainly, with lesions occasionally found on the eyelids, vulva, prepuce or anus.

The cause is unknown, although a bacterial component is suspected due to the response to antibacterial treatment.

Clinical findings

  • Any breed, sex, age – German shepherd may be predisposed. 
  • Swelling erythema of the lips initially.
  • Crusting and erosion with fissures may develop later.
  • Depigmentation of the lips may occur.
  • Care when examining as the lesions are often painful.

Diagnosis

  • Lesions extending along the length of the lips and involving the commissures are very suggestive.
  • The main differential diagnosis is lip fold pyoderma. There are no folds with mucocutaneous pyoderma and the lesions are more extensive. The two conditions could co-exist, complicating the diagnosis.
  • Other differential diagnoses include early autoimmune diseases such as pemphigus foliaceus or cutaneous lupus, demodicosis, Malassezia dermatitis, dermatophytosis and epitheliotropic lymphoma.

The diagnosis can be made on clinical grounds and response to treatment.

The finding of cocci and neutrophils in an impression smear of the lesions is supportive. Histopathological examination is confirmatory. Findings consist of epidermal hyperplasia, superficial crusting and a lichenoid dermatitis with preservation of the basement membrane. There is a dermal infiltrate consisting mainly of plasma cells with smaller numbers of lymphocytes, neutrophils and macrophages.

Treatment

  • Apply an Elizabethan collar if the dog is traumatising the lesions.
  • For mild cases a shampoo containing chlorhexidine applied daily for two weeks initially.
  • Mupirocin ointment applied twice daily has been suggested, and found to be very effective in some cases, although dogs may lick ointments and not tolerate touching of the lips. The dog illustrated would not tolerate topical treatment.
  • Systemic antibacterial treatment is therefore often needed, and in this case was four weeks of cephalexin at a dose of 30mg/kg every 12 hours. This achieved remission without relapse.

Relapse following treatment is not uncommon, however, and can be managed with topical treatment in the early stages, with the aim of maintaining control if cure is difficult. Although the lesions look inflamed, glucocorticoids are not necessary with the above treatment and may hinder the response.

Further reading

Hnilica, Keith A. (2011) Small Animal Dermatology. A Color Atlas and Therapeutic Guide. 3rd ed. pp57-58: Elsevier. 

David Grant, MBE, BVetMed, CertSAD, FRCVS, graduated from the RVC in 1968 and received his FRCVS in 1978. David was hospital director at RSPCA Harmsworth for 25 years and now writes and lectures internationally, mainly in dermatology.

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