Neutrophilic lymphadenitis is an uncommon cause of canine lymphadenomegaly, and is often related to infection. However, there is a small number of cases reported with sterile neutrophilic lymphadenitis. The aim of this study is to review a series of dogs with sterile neutrophilic lymphadenitis, who responded to immunosuppression.

Between 2006 and 2011, five cases were diagnosed with sterile neutrophilic lymphadenitis: two Cocker Spaniels, two English Springer Spaniels and one Border Collie. There were three entire female and one entire male Spaniel, while the Collie was male neutered. The median age at presentation was 16.8 months; only the Border Collie was older than 18 months (3y5m). All dogs were lethargic and had pyrexia (median 40.1°C, range 39.3–40.9). All dogs received antibiotics and non-steroidal anti-inflammatory drugs prior to referral but failed to improve. Two dogs presented with coughing, two with abdominal discomfort and one with marked submandibular swelling. Haematology revealed an inflammatory leucogram (neutrophils 16.3–34.7x10⁹/l) in all patients. Two dogs had a mild hypoalbuminaemia (21–24 g/l) and all had an elevated ALKP (133–1205 IU/l), while three dogs had mild fasting hypercholesterolaemia (10.4–11.0 mmol/l). Blood Borrellia and Bartonella PCR were negative in four tested dogs. Anaplasma phagocytophilum PCR was negative in the one tested dog. In 4 dogs enlarged mesenteric lymph nodes (0.8–3.6 cm diameter) were detected on abdominal ultrasound. Ultrasound confirmed the submandibular lymph node enlargement underneath the swelling in the other dog (3.6 cm diameter). Four dogs had thoracic radiographs, two were unremarkable, one had mild tracheobronchial lymphadenomegaly and one had a broncho-interstitial pattern. Both coughing dogs underwent bronchoscopy and BAL, which revealed marked neutrophilic inflammation without visible infectious cause; anaerobic and aerobic cultures were negative. Cytology of the mesenteric (4 dogs) or submandibular lymph nodes (1 dog) was consistent with neutrophilic lymphadenitis; culture (2 dogs) or ZN, PAS and Gram stains on lymph node biopsy (2 dogs) were negative. Four dogs received immunosuppressive prednisolone (2 mg/kg PO SID) and showed immediate clinical improvement, which was sustained during gradual reduction of prednisolone. Only one patient relapsed after being started on an anti-inflammatory dose of prednisolone, but went in remission on an increased dose.

Sterile neutrophilic lymphadenitis is a rare diagnosis and was mainly diagnosed in young dogs. Immunosuppressive treatment appears to be effective, and relapse is uncommon with appropriate immunosuppressive treatment.