Immune-mediated fever in the dog 169 pointer, a 5 year old female kleiner Münsterlän- der, a female Irish setter, a male Schiller dog and a female ﬂatcoated retriever. The latter 3 dogs were all in their ﬁrst year of life. In the fever, muscle and joint pain group (4 dogs) 1 Berner Sennen and 1 border collie tested positive for ANA and the Berner Sennen was also anti ENA positive. Serum from the Berner Sennen was not tested for IL-6 activity, but the other 3 dogs were tested and presented all elevated IL-6 activity. Antibodies against native DNA were not de- tected in any serum of 20 dogs with fever, and antibodies against DNP was only found in serum of one out of 12 dogs. This dog was a two-year-old male English setter in the fever and muscle pain group. He was also ANA pos- itive. All controls were negative for antibodies against native DNA and DNP. Sera from 18 controls and 15 patients were examined for TNF-α. All sera were negative. Discussion Infection seems unlikely to be the reason for the fever in this material. The clinical ﬁndings, the fact that no patients responded to antibiotic therapy, that many of them were ANA positive and all responded to immune suppressive doses of prednisolone, indicate that the fever and other clinical signs in these dogs were immune- mediated. This is further supported by that none of the patients during the past 2 years since the study was ended has shown evidence of another reason for the fever. The sex distribution in the present material was even, and except for the Schiller dogs, a breed which is uncommon in the present practice, no breed seemed to be over represented. Dunn & Dunn (1998) found a high percentage of springer spaniels, German shepherd dogs and border collies, less than one year old and famil- iarly related, showing immune-mediated fever and muscle and joint pain. The present study did not catch more than one border collie, but before the study started several young, famil- iarily related dogs of this breed had been ob- served in this practice with fever and muscle and joint pain. It is, however, evident that 9 out of 20 dogs in our material were 1 year or younger. Bennet & May (1995) have deﬁned criteria for diagnosis of immune-based arthropathies of dogs. The polyarthritis/polymyositis syndrome (PM) is deﬁned by presence of non-erosive pol- yarthritis, chronic active myositis in at least 2 muscle biopsies and negative for antinuclear antibodies. We ﬁnd it difﬁcult to ﬁt our patients into this system. From a clinical point of view it seems rational to classify most of them as hav- ing polyarthritis/polymyositis syndrome, but the fact that many of them are ANA positive, without showing signs of systemic lupus ery- thematosus, exclude them from any group. It may be relevant that our patients had only some few days disease history before they were examined and treated, and thus might have de- veloped additional signs if treatment had been delayed. The patients of Bennet & Kelly (1987) comprising 2 springer spaniels, 2 cavalier King Charles spaniels, 1 cocker spaniel and 1 whip- pet and sorted into the PM category had been sick for several weeks before they got their di- agnosis. The present study did not demonstrate anti DNA in serum from any patient. This is in ac- cordance with earlier investigations (Hansson & Karlsson-Parra 1999) examining sera from dogs with musculoskeletal disorders. The 2 inﬂammatory mediators, IL-6 and TNF- α are known to contribute in local inﬂamma- tory response and can have systemic effects. TNF-α was not detected in serum of any pa- tient. HogenEsch et al. (1995) studying juvenile polyarteritis syndrom (JPS), an idiopathic febrile disease affecting primarily beagles be- Acta vet. scand. vol. 43 no. 3, 2002