Two patients with arthritis of the knee joints associated with cutaneous polyarteritis have been followed for 20 and 5 years. The arthritis is characterized by mild to moderate pain and stiffness and inflammatory joint effusions with predominantly polymorphonuclear leukocytes. Despite its chronicity, there has been no clinical or radiologic evidence of joint destruction. Necrotizing inflammation was seen in arteries of the deep skin but not in the small vessels observed in the synovial biopsy specimens.Cutaneous polyarteritis is characterized by a variety of cutaneous lesions, a benign course, and necrotizing arteritis (1-3). The skin findings, which are often localized to the lower extremities, most frequently include painful erythematous nodules, ulcerations, and livedo reticularis. Cutaneous polyarteritis, however, is not strictly a cutaneous disorder, because arthralgia, arthritis and peripheral neuropathy, and fever may also occur. The generally benign course may be brief, protracted over many years, or episodic with spontaneous or corticosteroid-induced remissions (3). In many patients the white blood cell count and/or erythrocyte sedimentation rate is increased. Diagnosis is confirmed by an excision biopsy of the skin deep enough to detect necrotizing inflammation of arteries in the deep dermis or subcutaneous tissue. These histopathologic findings are identical with those of the skin lesions of systemic polyarteritis. However the predominant cutaneous findings, usual absence of visceral lesions, and benign course of cutaneous polyarteritis are the basis of its delineation from systemic polyarteritis (1-3)We have observed a chronic nondestructive arthritis of the knees in 2 patients with cutaneous polyarteritis for 20 and 5 years. This report describes the clinical features, light microscopic findings in the skin, and light and electron microscopic findings in synovial biopsy specimens of this unusual arthritis. Possible reasons for the benign nature of this joint disease are presented.
CASE REPORTS Patient AThis 68-year-old white man developed painful tender skin lesions over the legs and ankles at the outset of his illness, which has now persisted for 20 years. Hospital evaluation at onset showed that he was emaciated, febrile, and normotensive. There were multiple hemorrhagic, exquisitely tender, and indurated lesions measuring 1.5 to 2 cm in diameter over the anterior surface of the legs, the malleoli, and the dorsurn of the feet. Except for pitting edema which extended to the knees