Cutaneous and systemic necrotizing vasculitis in swine

A systemic vasculitis involving particularly the skin and kidneys has been recently described in swine under the name dermatitis/nephropathy syndrome. Twelve pigs with gross cutaneous lesions typical of this condition were ne cropsied, and morphologic, immunohistochemical, microbiologic, and epidemio logic characteristics were studied. The pigs were divided into three groups comprising eight pigs with acute lesions, two with chronic lesions, and tw o with acute lesions kept for sequential skin biopsies. Acute skin lesions consisted of round to irregular, red to purple macules and papules that oft en coalesced to form large, irregular patches and plaques. With time, the l esions became covered by crusts and faded gradually, sometimes leaving scar s. Characteristic distribution included the perineal area of the hindquarte rs, limbs, dependent parts of the abdomen and thorax, and margins of the ea rs. In the acute phase of the disease, necrotizing and leucocytoclastic vas culitis of small-caliber blood vessels were observed within the dermis and panniculus and in various extracutaneous locations such as the renal pelvis and synovial membranes. All pigs had macroscopic evidence of pneumonia and generalized lymphadenopathy. Microscopically, they had interstitial pneumo nia and perivascular cuffing of mononuclear cells in various tissues includ ing skin. The presence of immunoglobulins and complement was demonstrated b y immunofluorescence in and around necrotic vessels of the skin in the earl y stages. Porcine reproductive and respiratory syndrome (PRRS) virus (PRRSV ) antigens were detected by immunohistochemistry in macrophages located aro und vessels of the tissues examined (skin and kidneys) in acute and chronic cases. PRRSV RNA was demonstrated by reverse transcription-polymerase chai n reaction in lung and spleen homogenates from all pigs. The PRRSV was isol ated in cell culture from 11 of the pigs. These findings suggest that PRRSV infection may play a role in the pathogenesis of this systemic vascular di sease of swine.