Proliferative, Lymphocytic, Infundibular Mural Folliculitis and Dermatitis with Prominent Follicular Apoptosis and Parakeratotic Casts in Four Labrador Retrievers: Preliminary Description and Response to Therapy

The document reports on a novel skin disease in four Labrador retrievers, presenting with verrucous papules and plaques, hair loss, and comedones. Histopathological analysis showed hyperkeratosis, lymphocytic exocytosis, and keratinocyte apoptosis, with immunohistochemistry indicating a high number of CD3+ T lymphocytes and apoptotic cells. The cause was unclear but suggested to be an immune-mediated process. Treatment with immunosuppressive drugs like ciclosporin yielded complete remission in two dogs, partial and temporary improvement in one dog with prednisone, azathioprine, and ciclosporin, while one dog was untreated. The study, although limited by its small sample size of four dogs, suggests that the condition may be an immune response to unknown antigens on keratinocytes, similar to feline proliferative necrotizing otitis, and responds to immunosuppressive therapy.