In KD, myocarditis develops even earlier than epicardial coronary arteritis; it peaks by disease day 10 and then disappears gradually after day 20. The myocarditis is distributed unevenly, ranging from the entire heart to the epicardial layer of the base of the heart.

We speculate that endothelial dysfunction in former KD patients is affected by the febrile period of the acute phase, and antiplatelet drugs may improve endothelial function. The increased arterial stiffness of patients caused by post-inflammatory fibrotic changes in the arterial wall indicates that adults with a history of KD have an increased risk of developing atherosclerosis.

The pathogenesis of intussusception caused by enterohemorrhagic Escherichia coli (E. coli) O157 infection is unknown. In our case, colonoscopy was useful for confirming O157 infection. The intussusception was caused by focally damaged edematous mucosa in the cecum. This case helped in elucidating the pathogenesis of the disease.

A 7-month-old boy presented to the hospital with fever, vomiting, and appetite loss and was admitted with a diagnosis of dehydration due to gastroenteritis. Although he stopped drinking and eating, he continued to vomit. The day after admission, systolic murmur, tachypnea, and retractive breathing appeared, and echocardiography showed mitral regurgitation resulting from chordal rupture. Although the vomiting and pleural effusion were improved with medical therapy, retractive breathing persisted. Mitral valve plastic surgery was performed. Mitral valve chordal rupture in infants is rare and presents with nonspecific symptoms. Because most patients need surgical treatment, early and appropriate diagnosis is necessary.