Pododermatitis (Interdigital Dermatitis)
Dr. Rosanna Marsalla
The term pododermatitis is not a specific diagnosis. It simply means inflammation of the feet, and numerous diseases include involvement of the feet. Allergies can be present with itchy feet. Face and ears are also itchy and the dog tends to relapse with skin infections. Depending on the nature of the allergies, this could occur all year or only during certain times of the year. As a consequence of the itching, the feet tend to become swollen and infected. A rusty discoloration is present on feet that are chronically licked. This is called "salivary staining" and is caused by a substance present in the saliva of the animal. Allergies tend to worsen with age, so it is important to determine the exact cause in order to make your dog comfortable.
As different diseases require different therapies, it is very important to establish a correct diagnosis. The history, age of onset, progression of the disease, presence of other skin problems in other parts of the body, presence of pruritus (itching) and existence of concurrent systemic disease, are all factors that should be considered to differentiate among diseases and establish a correct diagnosis. Other diseases that may include pododermatitis include:
Auto-immune diseases like pemphigus and lupus can also manifest with a pododermatitis. Lesions are more severe than the those seen with allergies. The pads may become cracked, and the animal may be in pain when walking on hard surfaces. In most cases, other parts of the body are also affected, such as yellow crusts on face and ears, and the animal may feel depressed and have a poor appetite.
Internal diseases like pancreatic tumors or liver cirrhosis can also manifest with a pododermatitis. The pads become hard and cracked. Little sores may also be present around the mouth and on pressure points. Skin lesions may be evident months before other signs of systemic disease. This disease is diagnosed with a skin biopsy.
Fungal organisms are present in the soil of some areas, and animals may become infected by walking on contaminated areas. In those cases the nails may grow abnormally and become very friable. This is a mycosis that has the potential of being zoonotic, which means it can also infect humans, so early diagnosis is extremely important.
Mange can also manifest with pododermatitis. Two different types of mange occur. One is contagious to people and other animals (sarcoptic mange) while the second one is not contagious (demodicosis). Demodicosis commonly affects the feet, which may become very itchy and swollen. Secondary bacterial infections are also extremely common with this disease. Skin scrapings and biopsies may be necessary to diagnose the disease and determine the nature of the infection. When several feet are affected, prognosis is guarded. If your dog is less than 2 years of age, it is important that you consider neutering him, as this condition is hereditary. If your dog is older, an underlying disease may be present.
In rare cases, there may be sloughing of the nails, and the feet may become very painful. This could be due to auto-immune disease, drug reactions or a nail dystrophy. A biopsy is crucial to establish diagnosis.