Pododermatitis is a common inflammatory disease of the pedal skin of dogs. There is no specific age, sex, or breed disposition for the condition, although some breeds are considered to be more susceptible. Many internal and external factors may be directly or indirectly involved in the pathogenesis of pododermatitis, including infectious, hypersensitive, autoimmune, or endocrine diseases; environmental causes; hyperkeratotic, nodular, and pigmentary dermatoses; and psychogenic or neurologic causes. Clinical signs include diffuse erythema and thickening of the skin, and the primary lesions are often complicated by alopecia, hyperpigmentation, pyoderma, and the presence of sinus tracts with discharge. The disorder is often painful and pruritic, with resulting self-trauma that predisposes to secondary bacterial infection. Because treatment is largely influenced by the underlying cause, diagnostic investigation should include analysis of a detailed history, clinical examination, and appropriate testing. Depending on the underlying problem, prognosis can be good to guarded or poor. Even with a methodical diagnostic approach, an underlying cause may still remain obscure, prompting a diagnosis of idiopathic pododermatitis. Various theories have been proposed to explain this poorly understood condition, although many reports implicate bacterial infection with possible hair follicle-related pathology. The authors of this review article propose the term lymphocytic-plasmacytic pododermatitis among a subpopulation of dogs with idiopathic pododermatitis, based on the histologic appearance of the lesions. These cases appear to respond to immunomodulatory therapy, suggesting an underlying immunologic basis. Further studies on this subpopulation are being conducted by the authors.

COMMENTARY: This review article comprehensively discusses a frequently frustrating disorder. The article does not go into enormous detail on every possible cause, but from a clinical perspective, it offers much for clinicians -- including the numerous potential causes of pododermatitis and ways to help differentiate them through history, clinical presentation, and histopathologic appearance. Surprisingly, the authors have found only 0.5% of the dogs referred to their dermatology clinic to have idiopathic pododermatitis (other authors have cited higher percentages). They include an interesting discussion of their findings on a subpopulation of this group, and it will be intriguing to see what further insights into the disease their current research will provide. -- Jennifer L. Schori, VMD

Canine pododermatitis and idiopathic disease. Breathnach RM, Fanning S, Mulcahy G, et al. VET J Oct 3 2007.