Angiography was historically used to detect coronary artery aneurysms, and remains the gold standard for their detection, but is rarely used today unless coronary artery aneurysms have already been detected by echocardiography.Biopsy is rarely performed, as it is not necessary for diagnosis. Subtypes
Based on clinical findings, a diagnostic distinction may be made between the classic / typical presentation of Kawasaki disease and incomplete / atypical presentation of a "suspected" form of the disease. Regarding incomplete / atypical presentation, American Heart Association guidelines state that Kawasaki disease "should be considered in the differential diagnosis of prolonged unexplained fever in childhood associated with any of the principal clinical features of the disease, and the diagnosis can be considered confirmed when coronary artery aneurysms are identified in such patients by echocardiography. "A further distinction between incomplete and atypical subtypes may also be made in the presence of non-typical symptoms. Case definition
For study purposes, including vaccine safety monitoring, an international case definition has been proposed to categorize definite (i.e. complete/incomplete), probable and possible cases of Kawasaki disease. Differential diagnosis
The broadness of the differential diagnosis is a challenge to timely diagnosis of Kawasaki disease. Infectious and noninfectious conditions requiring consideration include: measles and other viral infections (e.g. adenovirus, enterovirus); staphylococcal and streptococcal toxin-mediated diseases such as scarlet fever and toxic shock syndrome; drug hypersensitivity reactions (including Stevens Johnson syndrome); systemic onset juvenile idiopathic arthritis; Rocky Mountain spotted fever or other rickettsial infections; and leptospirosis.
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.