Fulminant Streptococcus canis-associated necrotizing cellulitis requiring hindlimb amputation in an immunosuppressed dog with diabetes mellitus

A 6-year-old neutered male Pomeranian with diabetes mellitus receiving chronic multidrug immunosuppressive therapy was presented with rapidly progressive swelling and hemorrhagic discoloration of the left hindlimb. The dog had febrile neutropenia and distributive shock, and cytology revealed septic suppurative inflammation with intracellular cocci. Despite stabilization and broad-spectrum antimicrobial therapy, the lesion progressed proximally, prompting hindlimb amputation for source control. Histopathology confirmed severe necrotizing cellulitis with vasculitis, and Streptococcus canis was isolated from tissue and surgical-site exudate. Subsequent wound management included additional debridement of residual devitalized tissue and negative pressure wound therapy. The dog remained clinically well at the 61-day follow-up. This case illustrates that canine necrotizing cellulitis without fascial involvement can progress rapidly and require aggressive surgical source control.