Incomplete and atypical Kawasaki disease: a clinicopathologic paradox at high risk of sudden and unexpected infant death.

Incomplete Kawasaki disease (IKD) and atypical Kawasaki disease (AKD) represent rare conditions. Two cases of unexpected or sudden infant death are reported. The diagnosis for a 3-month-old girl was determined by echocardiography, and the child unexpectedly died despite appropriate treatment, whereas autopsy determined the diagnosis of AKD for a 4-month-old boy. In both patients, giant coronary artery aneurysms with thrombosis and vasculitis, myocarditis, and coagulative necrosis were shown at autopsy. These rare forms of IKD and AKD carry a poor prognosis and represent a paradox between the severe cardiovascular damage and the clinical presentation that mimics common and usually self-limiting exanthematic infectious disease in infancy.