What is pododermatitis?
Pododermatitis is a term used to describe inflammation of the feet or paws.
What causes pododermatitis?
Pododermatitis is inflammation that can be caused by many disorders including infections, allergies, hormonal disorders, immune-mediated diseases, tumors or cancers, and environmental contaminants.
Questions that may be asked in order to determine the cause or causes include the following:
- What is the general environment in which the dog walks and lives?
- Is there is seasonality to the clinical signs or do the symptoms last year-round?
- Are there additional lesions elsewhere on the body?
- What, if any, has the response to other treatments been?
- What is the dog's diet?
- Has the dog traveled anywhere outside its usual environment?
- Does the dog have any other medical problems?
What are the clinical signs of pododermatitis?
Clinical signs of pododermatitis are associated with the various causes:
Infectious. The feet and paws are often red (inflamed) and swollen. There may be nodules or fungal lesions (kerions), ulcers, or discharge (pus) from the lesions. There is often hair loss and the dog may lick the feet constantly.
Allergic. The feet are inflamed and swelling may be present. Itching is a constant problem with the tops of the paws most commonly involved. There is usually reddish brown staining of the fur from pigments naturally present in the saliva. In cases of contact pododermatitis (walking on or contacting an offensive substance), the undersides of the paws are usually involved, although the entire paw may be affected.
Immune-mediated. The most common clinical signs are crusts (scabs) and ulcerations with occasional blisters. All four feet are commonly involved, especially the footpads and nailbeds. Excessive darkening of the tissues and thickened, crusty footpads with erosive lesions may be present, especially in cases of pemphigus foliaceus.
Hormonal or metabolic. Lesions are usually caused by secondary skin infections and include pustules, redness, and inflammation.
Tumors. Usually only one foot is involved and there may be a nodule or one or more ulcers. Multiple feet may be involved in squamous cell carcinoma of the nailbed.
Environmental. One or more feet may be involved, depending on the cause or contact status. Most dogs experience chronic swelling between the toes, ulceration, abscesses, and discharge with or without itching.
How is the specific cause of pododermatitis diagnosed?
Diagnosis is based on medical history and clinical signs as well as skin cytology, skin scrapings, and hair pluckings. Cytology is used to look for the presence or absence of inflammatory cells, as well as bacteria, yeast, and parasites. Skin scrapings and hair pluckings evaluate for parasites including demodex mites. Additional tests may include bacterial and fungal cultures, biopsies, blood and urine tests, hypoallergenic food trials, and radiographs.
Some of the specific causes of pododermatitis include:
Bacterial - Staphylococcus, Pseudomonas, Proteus, Mycobacterium, Nocardia, and Actinomyces
Fungal - Dermatophytes (ringworm), sporotrichosis, mycetoma, blastomycosis, and cryptococcosis
Parasitic - Demodex canis (mange mite), Pelodera strongyloides (soil nematode) and hookworms
Atopy or seasonal allergies, food hypersensitivity, allergic contact dermatitis
Pemphigus foliaceus, systemic lupus erythematosus, erythema multiforme, toxic epidermal necrolysis, vasculitis, cold agglutinin disease, pemphigus vulgaris, and bullous pemphigoid
- Hormonal or Metabolic
Hypothyroidism, hyperadrenocorticism (Cushing's disease), hepatocutaneous syndrome (necrolytic migratory erythema - a rare condition)
Tumors of the foot (tumors however, are more common in cats than dogs).
Squamous cell carcinoma, melanoma, mast cell tumor, keratoacanthoma, inverted papilloma, eccrine adenocarcinoma
Irritant contact dermatitis, trauma, concrete and gravel dog runs, excessive exercise or running on hard surfaces, clipper burn, grass awns, foreign bodies, thallium toxicity
How is pododermatitis treated?
Because there are a number of potential causes for pododermatitis, a specific diagnosis is needed in order to develop a treatment plan.
Once the underlying cause is determined, treatment will be directed toward that cause. If the pododermatitis has an allergic or immune-mediated cause, it is important to note that the condition will not be cured. In these cases, the therapeutic goal is to minimize clinical signs and recurrences.
"Once a specific diagnosis is made, treatment will be directed toward that cause."
Treatments may include topical therapy such as shampoo washes, foot soaks, or wipes for secondary bacterial and yeast infections. Oral antibiotics and anti-fungals may be required for more severe cases. In addition, corticosteroids (e.g., prednisone) and immune modulating drugs (e.g., cyclosporine, brand name Atopica®) may be required in cases involving seasonal or food allergies.
What is the prognosis for pododermatitis?
The prognosis is dependent on the underlying cause. Most dogs respond well to therapy. With simple lifestyle adjustments, they go on to enjoy relatively normal lives.