Read the German translation: Pododermatitis Beim Hund

Introduction

Pododermatitis is a common, chronic, inflammatory skin disease of the feet with variable etiology. The clinical work up of pododermatitis may be lengthy and extensive. A step wise approach with diagnostic tests and diagnostic therapy and the response or lack of response to a diagnostic therapy ultimately leads to a diagnosis and cure or long term management. It is of utmost importance to find the underlying cause although this is not always possible. The clinical symptoms result from an etiological disease, secondary bacterial or Malassezia infections, environmental factors and the anatomy of the canine foot. Chronic inflammatory disease may ultimately lead to scar formation and malformation of feet. This may lead to a vicious circle of chronic inflammation.

Clinical Approach

Signalment

Hereditary diseases such as automutilation of feet (acral mutilation syndrome/ sensory neuropathy) are rare. Symptoms of excessive licking and biting start already in the first year of life and are described in the following breeds: French Spaniel, English Springer Spaniel, English Pointer and German shorthaired pointer.

With regard to the anatomy of feet it was reported that especially dogs with a flatter type of feet with marked interdigital webs (e.g., Labrador and Bulldogs) are more prone to chronic pododermatitis compared to dogs with more narrow feet like Border Collies or Greyhounds.¹

History

Pruritus: It is important to know whether the dog is pruritic, in which locations it shows pruritis (only feet or not), whether it is intensive or not and whether the pruritus started before the appearance of skin lesions or not. The presence of primary pruritus is more associated with parasitic diseases, allergic dermatitis or so called lymphoplasmacytic pododermatitis. Generally, dogs with pemphigus foliaceus have less intense pruritic disease or it may develop more during the course of the disease. Dogs with atopic dermatitis (cAD) or food adverse reaction may rarely have such intense pruritus that they bite at the margin of the foot pads inducing ulceration and secondary infections. Further symptoms such as otitis externa, systemic problems such as symptoms of GI disease give valuable information (flatulence, stool consistency and frequency of defecation, vomiting).

A history of staying abroad is key for including leishmaniosis or infection with non-indigenous parasites to the differential diagnosis.

Environment: In most countries hookworm infections may rarely cause pododermatitis. In a recent coprological study in Switzerland hookworms were regularly identified especially in dogs from rural areas.² Therefore information on the type of endoparasiticide and frequency of deworming belong to history taking. Deworming however does not exclude all parasitic infections.

Physical Examination

A thorough general and dermatological examination of the dog may give important clues to differential diagnoses of canine pododermatitis. This exam should include inspection of the mouth and ears.

Clues:

 Regional lymphadenopathy can occur due to the local inflammatory reaction, leishmaniosis and neoplasia.

 The general physical condition is often impaired in dogs with a hepatocutaneous syndrome.

 Lesions involving footpads indicate differential diagnoses of auto-immune diseases, hepatocutaneous syndrome or keratinization defects.

 In allergic diseases the dorsal or ventral side of the interdigital web is primarily involved. Besides erythema, hyperpigmentation or swelling, papules, nodules or fistulae oozing serohemorrhagic fluid may occur.

Diagnostic Tests

The minimal diagnostic screening should include deep skin scrapings, trichogram, cytology of the skin surface and possibly cytology of aspirated fluid from an intact pustule, vesicle, or nodule. Based on these findings a diagnostic therapy is started. Further diagnostic tests are depending on the clinical symptoms and differential diagnosis. A thorough orthopedic examination can be helpful in finding an underlying cause depending on the clinical signs. Skin biopsies are helpful in finding the etiologic cause. Even if an etiology is not found histopathological examination excludes differential diagnoses and may confirm a presumptive diagnosis (e.g., lymphocytic-plasmacytic pododermatitis). Table 1 summarizes the differential diagnoses of pododermatitis.

Table 1. Differential diagnoses of canine pododermatitis.

Idiopathic Pododermatitis

Despite a complete diagnostic workup it might be difficult to find an etiology for the pododermatitis. This remaining group has a heterogeneous background.⁴ These dogs have primarily interdigital lesions with pruritus, pain, swelling, erythema and alopecia. Lesions may include recurrent nodules and fistulae.

In these patients the following tests are all negative: deep skin scrapings, trichogram, cytology, diagnostic therapy for microbial infection, elimination diet and serum allergy test (SAT) and a general hematology and blood chemistry including T4 and cTSH determination. In histopathology most of these patients have a perivascular lymphoplasmacellular infiltration.

Many dogs show some improvement with a long course of antibiotics but only heal fully with prednisolone (starting dose 1.5-2 mg/kg/day and then tapered down) or cyclosporine (5 mg/kg/day). Most animals need lifelong management with reduced doses of prednisolone or cyclosporine and local therapy. Local therapy focuses on prevention and suppression of microbial growth. Weight reduction can be very beneficial. Early and aggressive therapy may prevent development of chronic changes and malformation of feet in which case dogs are more difficult to manage. Some dogs with recurrent nodules can benefit from laser therapy.

Treatment should fit the need of the individual patient and its owner. Until a steady state is reached regular checkups should be scheduled. It is beneficial to spend time on education of the owner on the duration and intensity of treatment and its prognosis.

References

1.  Whitney J. J Small Anim Pract 1970;11: 83.

2.  Sager H, et al. Parasitol Res 2006;98:333.

3.  Loeffler A, et al. Vet Dermatol 2007; 18:412.

4.  Breathnach RM, et al. Vet Dermatol 2005, 16: 364.