Occasionally, a cat will develop a small red sore on the edge of its upper or lower lip. This is what we refer to as a, indolent or Rodent Ulcer. In this case, rodent does not refer to a mouse, but is just one of several skin conditions that falls under a category called Eosinophilic granulomas. Lower lip ulcers are often called linear ulcers.
The photo on the right shows a close-up of a two-year old lynx point female Himalayan’s mouth. The red arrow points to a rodent ulcer that has developed on the lower lip. In this case the rodent ulcer is seen as a small, clearly defined sore right on the lip line.
An ulcer usually occurs where the skin joins the lining membrane of the mouth. The edges of the ulcer are hard and raised and the broken skin is irregular. The affected part is localized but may gradually become larger if untreated. It is usually found between the mid-line cleft of the lip and the canine tooth on the upper lip. The problem may occur on one side or both and occasionally may be seen elsewhere.
An Exotic Shorthair With Rodent Ulcer
The photo on the left shows a seven-month-old Exotic male who probably developed the classical rodent ulcer but it went untreated for some time before his owners noticed a problem. The first signs they noticed were not actually the pinkness around his mouth but that the cat was licking his lips more than usual and occasionally seemed like his lips were itchy.
His lower jaw and chin have been shaved to better view the problem. Both upper lips and most of his lower mouth are involved. Because ulcers can also develop on the cat’s tongue, always check inside the mouth too. While this boy looks unhappy, his objection is to being examined, not pain from the ulcer.
Rodent ulcers can look painful, but they usually are not and cause a cat no distress, not even affecting their enthusiasm for eating.
Taking a closer look at our patient’s mouth, you can see that the appearance from the outside is a pinkish, sore-looking area around his lips. While there has been some thinning of the hair near the lip line, there has not been a significant hair loss — except from shaving :-).
The cat was presented to his veterinarian because his owners noticed the external redness. They were quite shocked to see how extensive the problem was when their veterinarian opened the kitty’s mouth.
With the mouth open, you could see clearly how the ulcers have developed along the entire lip margins, actually merging together. The yellow arrow is pointing to an especially deep area of ulceration on the bottom lip which was likely where the ulcer first developed, even though it is unusual for a rodent ulcer to occur on a lower lip. Although this case of rodent ulcer is unusually extensive, the cat did not have ulcers on its tongue.
This cat’s condition responded well to two injections of the corticosteroid, Depo-Medrol two weeks apart. The ulcers went away quickly and did not returned.
The smaller ulcer on the Himalayan in the first photo at the top of this page was only treated with the antibiotic, Tribrissen 120mg, once daily for 10 days. It healed and never returned.
While unsightly, a rodent ulcer is not painful and usually responds well to a simple injection of a corticosteroid. If you discover a sore on your cat’s lip, take it immediately to be examined by your vet.