Clinicopathologic characterization of canine juvenile cellulitis.

The syndrome of canine juvenile cellulitis was observed and characterized throughout its clinical course when it occurred spontaneously in a litter of dogs. Histologically, pyogranulomatous inflammation was seen in facial skin and mandibular and superficial cervical lymph nodes of affected dogs. The predominant inflammatory cell characterized by light and electron microscopy and by immunohistochemical staining was an epithelioid macrophage. The same pyogranulomatous inflammatory process was seen in a lymph node anatomically distant from the site of apparent disease. Interestingly, a littermate with neither clinically evident dermal lesions nor lymphadenopathy had histologic evidence of a milder, but similar inflammatory process in a mandibular lymph node. The observation of canine juvenile cellulitis in clusters of dogs between 1 and 4 months of age and its apparent systemic nature suggest an infectious etiology. Bacterial, fungal, or viral agents were not isolated from affected lymph nodes. Attempts to transfer the disease by inoculation of neonatal puppies with tissue from affected dogs were also unsuccessful.