PATHOLOGICAL FEATURES OF NATURALLY-OCCURRING JUVENILE POLYARTERITIS IN BEAGLE DOGS

Eighteen young Beagle dogs (eight males and 10 females), ages 6-40 mon ths, with canine juvenile polyarteritis syndrome (CJPS), a naturally o ccurring vasculitis and perivasculitis of unknown etiology, were necro psied, and their tissues were examined by histopathologic and histoche mical methods. The condition is characterized by recurring episodes of an acute onset of fever (>40 C) and neck pain that persist for 3-7 da ys. The major histopathologic alterations were a systemic vasculitis a nd perivasculitis. During the febrile, painful period of CJPS, the vas cular lesions ranged from a histiocytic-lymphocytic periarterial infil tration to transmural arterial inflammation with concomitant fibrinoid necrosis and vascular thrombosis. Massive periarterial accumulations of inflammatory cells were common and often extended into adjacent tis sues. The small- to medium-sized muscular arteries of the heart, crani al mediastinum, and cervical spinal meninges were consistently involve d. Vasculitis occasionally occurred in other organ systems. The vascul ar lesions in dogs examined during clinically normal periods consisted of intimal and medial fibrosis, ruptured elastic laminae, and mild pe rivasculitis; these lesions were probably related to previous episodes of vasculitis. Eight dogs that had experienced repeated acute episode s also developed splenic, hepatic, and renal amyloidosis. The clinical signs, laboratory abnormalities, and the vascular lesions suggest tha t the condition may be immune-system mediated. CJPS may serve as a nat urally occurring animal model of human immune-system-mediated vasculit ides such as polyarteritis nodosa, infantile polyarteritis, and Kawasa ki disease.