Mucocutaneous pyoderma

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.