Topical application of 0.1% tacrolimus ointment for treatment of sinus refractory pododermatitis secondary to atopy in a dog

An 8-year-old, castrated male Shih-tzu was referred due to relapsing pododermatitis and generalized pruritus. On physical examination, right forepaw showed swelling and serosanguinous exudates from sinus tract on dorsal paw. There were no remarkable findings on complete blood count (CBC), serum chemistry, and radiologic examination. On cytological examination of exudates from sinus tract, phagocyted bacteria and numerous degenerative neutrophils were noted. Results of deep skin scraping and plucking hair examination were unremarkable. Skin biopsy was performed and ruled out other skin diseases. Histopathology showed epidermal hyperplasia and diffuse mononuclear cell inflammation in dermal layer. Moreover, pyogranulomatous inflammation was demonstrated in subcutaneous layer. This case was clinically diagnosed as pododermatitis secondary to atopic dermatitis (AD). Clinical signs of pododermatitis were gradually improved following topical application of tacrolimus 0.1% ointment. This case report describes that tacrolimus ointment can be applicable for the treatment of refractory pododermatitis.