INDOLENT ulcer (from Latin indolens – without pain) is a common lesion in cats and is considered part of the eosinophilic granuloma complex, one of the feline cutaneous reaction patterns.
An older term, “rodent ulcer”, is best avoided, as this is a malignant tumour in humans whereas the indolent ulcer in cats is an inflammatory lesion. It occurs on the ventral part of the upper lip and is a painless ulcerative lesion caused by the cat licking. Initially the lesion may present as a mild thickening of the lip with a superficial ulceration (Figure 1). Without treatment the lesions become more extensive and disfiguring (Figures 2 and 3). They may be unilateral or bilateral.
Causes
- Most cases of indolent ulcer are caused by hypersensitivity disorders.
- Of the hypersensitive disorders, incriminated fleabite hypersensitivity is the most important, followed less commonly by atopic dermatitis and food hypersensitivity/intolerance.
- Bacterial involvement may occur secondarily or occasionally as a primary cause.
Differential diagnosis
Differential diagnosis includes those hypersensitivity disorders already mentioned. In addition:
- bacterial infection;
- fungal diseases;
- viral diseases;
- neoplasia (squamous cell carcinoma, mast cell tumour, lymphoma).
Diagnosis
- History and physical examination. The site of the lesion is typical. Indolent ulcer may co-exist with other cutaneous reaction patterns associated with hypersensitivity disorders, particularly fleabite hypersensitivity (miliary dermatitis, symmetrical alopecia).
- Cytology. A cytological preparation can be obtained via a direct impression smear, and also following light scarification of the lesion. The presence of bacteria intracellularly in neutrophils indicates infection. Eosinophils are not invariably present.
- Biopsy. In typical cases this is not always necessary. Histopathological findings are variable, and include superficial perivascular dermatitis and fibrosis. Inflammatory cells are primarily neutrophils and mononuclear cells; eosinophils are not typically found (Hnilica, 2011). Biopsy is most useful to rule out neoplasia if doubt exists clinically.
- Response to treatment resulting in cure and prevention of recurrence.
Treatment
If bacterial involvement is suggested by cytology, antibacterial therapy may be initiated for 3 to 4 weeks. Some cases have been reported to respond to antibacterial therapy as the sole treatment (Miller, Griffin and Campbell, 2013).
- Suitable antibacterial agents include clindamycin 11-22 mg/kg once daily, clavulanic acid potentiated amoxicillin 12.5 mg/kg every 12 hours and doxycycline 5-10 mg/kg every 12 hours.
- For the majority of cases that have an underlying hypersensitivity disorder, glucocorticoids or cyclosporine are effective remission inducing treatments prior to investigating the underlying cause.
- Prednisolone is given at a dose of 2mg/kg every 12 hours reducing over 3 to 4 weeks to the lowest possible alternate day dose.
- In those cases that fail to respond, dexamethasone may be effective. It is given at a dose of 2mg daily tapering over a period of 3 to 4 weeks to 2mg every 3 days.
- Cyclosporine is effective at an initial dose of 7.5mg/kg tapering to the same dose every 48 to 72 hours. Many cats can be maintained on every 72 hour dosing (Hnilica, 2011). Cats receiving this treatment should be tested for FIV and FeLV viruses. There is a small increased risk of Toxoplasma-negative cats acquiring the infection if they hunt small birds and rodents.
- A comprehensive flea control treatment should be started at the same time as anti-inflammatory therapy. It is important to induce remission, then continue the flea control alone to ascertain whether flea control prevents relapse. If remission is not first achieved, the itch-lick cycle will make establishment of the underlying cause difficult. Consider flea treatments with a rapid kill so that fleas only get one bite before they die. Absolute flea control is not possible during the warm humid months of the year if the cat is allowed outside. Those cats with fleabite hypersensitivity as an underlying cause should remain in remission during the cold months of the year without anti-inflammatory treatment if flea control has been comprehensive and there are no fleas or life cycle stages in the cat’s environment.
- If flea control does not induce remission, anti-inflammatory treatment is repeated along with a food allergy trial with a commercial hydrolysed diet for 6 to 8 weeks. Commercial diets improve compliance and are nutritionally balanced. If remission is not maintained with the diet once anti-inflammatory treatment is stopped for two weeks, food intolerance is effectively ruled out and the most likely hypersensitivity disorder causing the indolent ulcer is atopic dermatitis.
- Underlying atopic dermatitis and/ or undiagnosed hypersensitivity may be managed with glucocorticoids or cyclosporine at the lowest possible doses as previously discussed.
References
Miller, W. H., Griffin, C. E. and Campbell, K. L. (2013) In: Muller & Kirk’s Small Animal Dermatology pp716-718. Elsevier.
Hnilica, K. A. (2011) In: Small Animal Dermatology A Color Atlas and Therapeutic Guide pp213-215. Elsevier.
