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Feline fat chin syndrome

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01 June 2014, at 1:00am

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.