Kawasaki disease (KD) was first described in 1967 by Kawasaki, who defined it as ?mucocutaneous lymph node syndrome?. KD is an acute systemic vasculitis, which mainly involves medium calibre arteries; its origin is unknown, and it is observed in children under the age of 5, especially in their third year. The principal presentations of KD include fever, bilateral nonexudative conjunctivitis, erythema of the lips and oral mucosa, changes in the extremities, rash, and cervical lymphadenopathy. Within KD, oral mucositis ? represented by diffuse mucous membrane erythema, lip and tongue reddening and lingual papillae hypertrophy with subsequent development of strawberry tongue ? can occur both in the acute stage of the disease (0-9 days), and in the convalescence stage (>25 days) as a consequence of the pharmacological treatment. KD vascular lesions are defined as systemic vasculitis instead of systemic arteritis. This study analyzed the anatomical-pathological substrata of oral mucositis in a baby affected by Kawasaki disease and suddenly deceased for cardiac tamponade caused by coronary aneurysm rupture (sudden cardiac death of a mechanical type).