Papulonodular Dermatoses in Cats

Papulonodular dermatoses have several different causes, ranging from bacterial and fungal infection to inflammation and cancer. Cats who are suffering from diseases or taking medications that suppress the immune system have a predisposition for developing papulonodular dermatoses.

Papulonodular dermatoses is the technical name for any skin condition in cats in which papules or nodules appear on the skin’s surface. Papules are small bumps that are smaller than 1cm. Nodules are bigger than papules and are rooted in deep skin layers. These bumps are usually dry and do not emit pus.

While papulonodular dermatoses are not generally serious, you’ll need to contact a vet to relieve your cat’s discomfort. Do not rely on home treatments as these may not help an underlying cause. Look out for the following symptoms:

• Hair loss
• Excessive itching
• Lesions present on the skin
• Red or inflamed skin
• Crust formed on the skin

The cause of most papulonodular dermatoses is an underlying condition or infection, such as:

• Bacterial folliculitis: bacterial infection of the hair follicles
• Sepsis: secondary bacterial infection that has progressed into a serious condition
• Dermatophytosis: fungal infection of the skin, hair, or nails
• Kerions: nodules which ooze pus as the result of a fungal infection
• Rhabditic dermatitis: inflammation caused by a skin parasite
• Sebaceous adenitis: inflammation of the oil glands in the fur
• Sterile eosinophilic pustulosis: a condition in which white blood cells responsible for regulating allergic responses are present in the skin bumps
• Demodectic mange: a type of contagious mange caused by certain species of mites

Other causes may include conditions caused by overexposure to the sun or UV light, acne, and cancer. Cats with a white coat have a predisposition of developing sun-related skin conditions due to a lack of pigmentation.

The vet will be able to make a tentative diagnosis based on presentation of symptoms and appearance of the bumps. Be sure to inform your vet of your cat’s outdoor activity, any medications they are taking (particularly if they are on any immunosuppressants), and a complete medical history.

Diagnostic tests include skin scrapings, fungus and bacteria cultures, CT guided fine needle aspiration, and skin biopsy. These will determine the underlying cause of the dermatosis as well as the recommended course of treatment.

Treatment methods will vary based on the underlying cause. Most cats are treated on an outpatient basis and will be able to return home the same day. Treatment for papulonodular dermatoses generally involves the use of drug therapy. Antibiotics are typically used to treat cases caused by bacterial infection. Antibiotics may be prescribed for three to eight weeks depending on the cause. Vitamins or other medications, such as steroids or oral antifungal tablets, may also be prescribed. Drugs to boost the immune system may also be required in cases caused by suppressed immune systems.

Mild instances of feline acne may resolve without treatment. However, recurring or serious cases may require topical treatment, antibiotics, or other skin medications. Some of these treatments may irritate the skin. Your vet will be able to prescribe an acne medication based on your cat’s needs.

If the cause is sebaceous adenitis, the recommended course of treatment is a prescription spray (a solution of propylene glycol diluted with water). This spray is generally applied once per day, but your vet will be able to advise you on a dosage. Certain topical treatments are also available for many papulonodular dermatoses, including medicated shampoos, rinses, and moisturizers. These are prescribed by a vet and should not be purchased on an over-the-counter basis unless specifically directed by your vet.

In cases of demodectic mange, sepsis, and skin cancer, your cat may require surgery, hospitalization, or chemotherapy. Your vet will be able to advise you if this is necessary.

Recovery and prognosis depend on the underlying cause of papulonodular dermatoses. Always follow your vet’s post-treatment instructions carefully.

For most mild cases, activity and diet changes are not usually necessary. If your cat has been placed on an antibiotic regimen, it is imperative that you continue to administer the medication for the entire duration of the recommended treatment period even if the symptoms start to resolve. Failure to do so may result in aggressive recurrence. If your cat is undergoing chemotherapy to treat cancer, your vet may prescribe a special diet to combat appetite loss.

Note that certain types of fungal infections, particularly dermatophytosis, are contagious and may spread to humans. If you notice any lesions on your own skin after your cat has been diagnosed, contact your doctor immediately.

Your vet will schedule a follow-up appointment to monitor your cat’s condition and ensure the infection has cleared up. A number of follow-up tests may be used, including bacterial and fungal cultures, blood chemistry profile and analysis, urinalysis, and skin scrapings.