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 angiitis), 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 involving necrotizing vasculitis include polyarteritis nodosa, granulomatosis with polyangiitis, Henoch–Schönlein purpura, and eosinophilic granulomatosis with polyangiitis.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 100 µm in diameter. Kawasaki disease 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 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 can also be classed as an autoimmune form of vasculitis. It is not associated with anti-neutrophil cytoplasmic antibodies, unlike other vasculitic disorders associated with them (such as granulomatosis with polyangiitis, microscopic polyangiitis, and eosinophilic granulomatosis with polyangiitis). This form of categorization is relevant for appropriate treatment.
The criteria are:
erythema of the lips or oral cavity or cracking of the lips
rash on the trunk
swelling or erythema of the hands or feet
red eyes (conjunctival injection)
swollen lymph node in the neck of at least 15 mmMany children, especially infants, eventually diagnosed with Kawasaki disease, do not exhibit all of the above criteria. In fact, many experts now recommend treating for Kawasaki disease even if only three days of fever have passed and at least three diagnostic criteria are present, especially if other tests reveal abnormalities consistent with Kawasaki disease. In addition, the diagnosis can be made purely by the detection of coronary artery aneurysms in the proper clinical setting. Investigations
A physical examination will demonstrate many of the features listed above. Blood tests

Complete blood count may reveal normocytic anemia and eventually thrombocytosis. Erythrocyte sedimentation rate will be elevated. C-reactive protein will be elevated. Liver function tests may show evidence of hepatic inflammation and low serum albumin levels.Other optional tests include:

Electrocardiogram may show evidence of ventricular dysfunction or, occasionally, arrhythmia due to myocarditis. Echocardiogram may show subtle coronary artery changes or, later, true aneurysms. Ultrasound or computerized tomography may show hydrops (enlargement) of the gallbladder. Urinalysis may show white blood cells and protein in the urine (pyuria and proteinuria) without evidence of bacterial growth. Lumbar puncture may show evidence of aseptic meningitis.