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InFocus

Mucocutaneous pyoderma

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

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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