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Feline fat chin syndrome

David Grant continues the series of dermatology briefs

THE feline eosinophilic granuloma
complex (EGC) is a description
of a group of skin lesions seen
commonly in cats. It is one of
the major cutaneous reaction
patterns in the cat and should not
be considered a
diagnosis.

Those lesions
comprising the
complex are:

  • Indolent ulcer
    (formerly known as “rodent ulcer”);
  • Eosinophilic plaque;
  • Eosinophilic granuloma.
    Indolent ulcers occur on the
    inner surface of the upper lips.

Eosinophilic plaques often occur on
the ventral abdomen and medial thigh.
Eosinophilic granulomas can be quite
variable in their appearance.

They are often found on the backs
of the thighs in a linear fashion (linear granuloma). Other
sites include the
face, particularly
the pre-auricular
alopecia area, the chin (fat chin
syndrome), the pads and the oral cavity.

EGC lesions may appear as solitary
lesions or sometimes two or three
different lesions of the complex occur
on the same cat.

EGC lesions are most commonly the
result of an underlying hypersensitivity
to fleas (the most important cause),
food and mosquitoes. Bacteria may be
involved particularly as a secondary
component. Viral causes are rare and
some cases are idiopathic.

When chin lesions appear they
are often the only lesion and may
appear overnight prompting an early
presentation to the veterinary clinic.
Fat chin lesions typically consist of
swelling, oedema, erythema and hair
loss. The lesions are
not usually painful or pruritic and are
soft on palpation.

Differential diagnosis

  • Bacterial causes – such as feline acne;
  • Neoplasia.

Diagnosis

  • History and physical examination.
    Inspection of the oral cavity is
    important as typical eosinophilic
    granuloma lesions may occasionally be
    found on the soft palate, hard palate or
    tongue.
  • Cytology – impression smear.
    Eosinophils are present. Neutrophils
    and bacteria may be found in chronic
    cases that have become secondarily
    infected.
  • Histopathology. Histopathological findings are characteristic and
    include nodular or diffuse granuloma
    with eosinophils, histiocytes and
    multinucleated giant
    cells. Biopsy is not
    always necessary
    initially and can be
    reserved for those
    cases not responding
    to treatment.

Treatment

  • If bacterial
    infection is found
    on cytological
    examination
    a course of
    antibacterial therapy
    is necessary. Amoxicillin/clavulanate
    or cephalexin for three weeks usually
    suffices.
  • Fat chin syndrome in the absence
    of bacteria usually responds rapidly
    to a short course of glucocorticoids. Prednisone at a dose of
    1-2mg/kg will reduce the chin size to
    normal within a week or so. In order
    to maintain this remission attempts
    should be made to identify underling
    allergens.
  • A thorough flea eradication
    programme is an essential starting
    point.
  • If relapse occurs in spite of
    comprehensive flea control, the next step is investigation
    of the possible role of
    food. This involves a
    6-8 week food trial with
    a hypoallergenic diet
    followed by challenge
    if the diet succeeds in
    maintaining remission.
  • Feline atopy is a
    default diagnosis
    after ruling out other
    underlying causes.
  • In idiopathic cases
    alternate low dose
    glucocorticoids or cyclosporine (Atopica, Novartis) are
    effective long term. Some idiopathic
    cases appear intermittently and can
    be managed with short courses of
    glucocorticoids with minimum risk of
    side effects.