Classification
Systemic vasculitis is an inflammatory condition affecting both veins and arteries throughout the body, and is usually caused by a proliferation of cells associated with an immune response to a pathogen, or autoimmunity. Systemic vasculitides may be classified according to the type of cells involved in the proliferation, as well as the specific type of tissue damage occurring within the vein or arterial walls. Under this classification scheme for systemic vasculitis, Kawasaki disease is considered to be a necrotizing vasculitis (also called necrotizing angeititis), which may be identified histologically by the occurrence of necrosis (tissue death), fibrosis, and proliferation of cells associated with inflammation in the inner layer of the vascular wall. Other diseases featuring necrotizing vasculitis include Polyarteritis nodosa, Wegener's granulomatosis, Henoch-Schönlein purpura, and Churg-Strauss syndrome. Kawasaki disease may be further classified as a medium-sized-vessel vasculitis, affecting medium and small sized blood vessels, such as the smaller cutaneous vasculature (veins and arteries in the skin) that range from 50 to 100µm in diameter. KD is also considered to be a primary childhood vasculitis, a disorder associated with vasculitis that mainly affects children under the age of 18. A recent, consensus-based evaluation of vasculitides occurring primarily in children resulted in a classification scheme for these disorders, to both distinguish them and suggest a more concrete set of diagnostic criteria for each. Within this classification of childhood vasculitides, Kawasaki disease is, again, a predominantly medium-sized vessel vasculitis.
It is also an autoimmune form of vasculitis, and is not associated with ANCA antibodies, unlike other vasculitic disorders associated with them, such as wegener's granulomatosis, microscopic polyangiitis, and Churg-Strauss syndrome. This categorization is considered essential for appropriate treatment.
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