Also known as lymphocytic-plasmacytic gingivitis-stomatitis-pharyngitis (GSPC), stomatitis is a common disease-causing chronic inflammation and ulceration of the soft tissues in the mouth.
There is no definitive cause but it is felt to be multifactoral with an immune-mediated component, possibly representing a hypersensitivity to oral bacterial antigens.  Other possible factors include oral irritants, some viruses, immunodeficiency diseases, metabolic diseases, drug reactions etc.
Signs of stomatitis depend on the severity of the lesions, naturally, it can cause severe pain in the affected cat. Stomatitis most commonly begins in the fauces, which is the area in the back of the mouth where the lower jaw meets the upper jaw. This becomes red, swollen and ulcerated. Other symptoms include:
A complete physical examination and medical history can help in the diagnosis of stomatitis. Tests your veterinarian may recommend include:
Oral biopsy – A biopsy may be performed to determine if the lesions are caused by other diseases such as neoplasia (cancer) or eosinophilic granuloma complex. Biopsy should reveal a dense infiltration of lymphocytes and plasma cells.
FIV and FeLV test – Retroviral infections can lead to inflammatory oral disease.
Biochemical profile to rule out other conditions which may have a similar appearance to stomatitis.
X-ray – To check the condition of the dental roots and bones. Stomatitis often affects the molars and pre-molars more than the canines and incisors.
Stomatitis is very difficult to treat and response to many treatments are poor.
If the cause can be identified, then specific therapy can be aimed at treating or managing the problem, as indicated.
Professional cleaning of the teeth under anaesthesia is necessary, as a periodontal disease may cause or at least contribute to stomatitis.
Antibiotics given long term may be of benefit.
Cats unresponsive to treatment may require extraction of all teeth behind the canines to provide long-term relief. This may sound extreme but your cat will get along just fine without these teeth with the assistance of a softer diet.
Clean the cat’s teeth daily at home to keep plaque under control.
1: The Feline Patient – Gary D. Norsworthy, Mitchell A. Crystal, Sharon K. Fooshee and Larry P. Tilley.