Pyogranulomatous lymphadenitis with Splendore-Hoeppli phenomenon caused by Neisseria species in a domestic shorthair cat.

Neisseria species can cause feline pyogranulomatous lymphadenitis and may resolve with amoxicillin-clavulanate guided by susceptibility testing.

This case report describes a rare presentation of pyogranulomatous lymphadenitis caused by a Neisseria species in an 11-year-old male neutered domestic shorthair cat. The patient presented with right mandibular and prescapular lymphadenomegaly accompanied by weight loss. Diagnostic workup included fine-needle aspirate cytology, which revealed pyogranulomatous inflammation in the mandibular lymph node and mild neutrophilic, non-septic inflammation in the prescapular lymph node. Excisional biopsy of both lymph nodes was performed for histopathological evaluation and bacterial culture. Histopathology of the mandibular lymph node demonstrated severe pyogranulomatous inflammation with prominent Splendore-Hoeppli phenomenon — an eosinophilic, amorphous material surrounding microorganisms, indicative of a host immune response. The prescapular lymph node showed reactive lymphoid hyperplasia. Bacterial culture from both lymph node tissue samples yielded a Neisseria species, an uncommonly reported feline pathogen. Antimicrobial susceptibility testing confirmed sensitivity to amoxicillin-clavulanate, and the cat was treated with a 4-week oral course at 20 mg/kg PO q12h. Complete clinical resolution was achieved, with no evidence of recurrence at 2.5-year follow-up. This case highlights Neisseria species as an uncommon but treatable cause of feline lymphadenitis, underscores the diagnostic value of tissue culture and histopathology in pyogranulomatous lymph node disease, and demonstrates the importance of antimicrobial susceptibility testing to guide effective therapy.

This summary was distilled by AI and may occasionally misinterpret data. Confirm critical details with the primary literature before clinical application.