New algorithm (KAWAKAMI algorithm) to diagnose primary cutaneous vasculitis

AbstractPalpable purpura tends to indicate involvement of small vessel vasculitis in the upper dermis. Livedo racemosa, nodular lesion and skin ulceration are indicative of involvement of small to medium‐sized vessel vasculitis in the lower dermis to subcutaneous fat. We set out to establish a new algorithm (KAWAKAMI algorithm) for primary cutaneous vasculitis based on the Chapel Hill Consensus Conference classification and our research results, and apply to the diagnosis. The first step is to measure serum antineutrophil cytoplasmic antibodies (ANCA) levels. If myeloperoxidase‐ANCA is positive, Churg–Strauss syndrome or microscopic polyangiitis can be suspected, and if the patient is positive for proteinase 3‐ANCA, Wegener’s granulomatosis is most likely. Next, if cryoglobulin is positive, cryoglobulinemic vasculitis should be suspected. Third, if direct immunofluorescence of the skin biopsy specimen reveals immunoglobulin A deposition within the affected vessels, Henoch–Schönlein purpura is indicated. Finally, the presence of anti‐phosphatidylserine–prothrombin complex antibodies and/or lupus anticoagulant and histopathological necrotizing vasculitis in the upper to middle dermis (leukocytoclastic vasculitis) indicates cutaneous leukocytoclastic angiitis, whereas if necrotizing vasculitis exists in the lower dermis and/or is associated with the subcutaneous fat, cutaneous polyarteritis nodosa is indicated. The KAWAKAMI algorithm may allow us to refine our earlier diagnostic strategies and allow for efficacious treatment of primary cutaneous vasculitis. In cutaneous polyarteritis nodosa, warfarin or clopidogrel therapies should be administrated, and in cases that have associated active inflammatory lesions, corticosteroids or mizoribine (mycophenolate mofetil) therapy should be added. We further propose prophylactic treatment of renal complications in patients with Henoch–Schönlein purpura.