1. Severe RV results from a systemic arteritis of small to medium arteries. Histological-ly, this is a leukocytoclastic vasculitis with endothelial swelling, polymorphonuclear leukocyte invasion of vessel walls with necrosis, leukocytoclasis, and extravasation of red blood cells. Peripheral neuropathy presenting as mononeuritis, mononeuritis multiplex, or distal symmetric neuropathy may be the first sign. Neuropathy is assumed to result from vasculitis of the vasa nervorum. Gangrene of the digits, nailfold thromboses and infarcts, and deep cutaneous ulcers can also be seen.
Less common manifestations of this larger vessel vasculitis include ischemic bowel disease, cerebral vasculitis, pulmonary vasculitis, and vasculitic glomerulonephritis.
2. Moderate RV results from limited small vessel vasculitis involving the postcapillary venules. Histopathologically, it is also a leukocytoclastic vasculitis. Patients most often present with cutaneous lesions, most characteristically, palpable purpura, on dependent sites. Cutaneous small-vessel vasculitis can be seen in many disease states and can be caused by infection, drugs, foreign protein, or immune complexes (autoimmune diseases). Moderate RV is believed to be an immune complex-mediated vasculitis in patients with high-titer RF that represents IgM (or IgA)/IgG immune complexes.
3. Mild RV describes cutaneous manifestations of RA that occur in the absence of systemic vasculitis, and includes nailfold teleangiect-asias with thromboses, minute digital ulcerations (Fig. 5), digital petechiae, livedo reticularis, and digital pulp papules also known as Bywaters lesions. Bywaters lesions are purpuric papules that primarily affect the pulp of the distal digits. Histopathologic examinations of these lesions again reveals le-ukocytoclastic vasculitis. Bywaters lesions
differ from rheumatoid nodules in that no palisading granulomatous response is found in histologic specimens.
Features of cutaneous RV overlapping both the characteristics of cutaneous necrotizing venulitis and cutaneous polyarteritis nodosa together with coexistence of these different type of vasculitis in the same or different lesional skin account for the associated diverse cutaneous vasculitic manifestations. Although dermal venulitis (leucocytoclastic vasculitis) was the most common presentation, the presence of leucocytoclastic vasculitis in rheumatoid patients did not necessarily indicate a favourable prognosis (Voskuyl et al., 1996a; Crowson et al., 2003). Associations with mononeuritis multiplex and bowel involvement had a fatal prognosis, while patients with superficial dermal venulitis without other extra-articular involvement may follow a favourable prognosis (Voskuyl et al., 1996b).
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