Histopathological characteristics of myocarditis in acute-phase Kawasaki disease

Area of Science:

• Cardiovascular Pathology
• Pediatric Infectious Diseases
• Immunohistochemistry

Background:

• Kawasaki disease (KD) is an acute febrile vasculitis affecting medium-sized arteries, primarily the coronary arteries.
• Myocardial involvement in KD is recognized but its histopathological timeline and distribution remain less understood.
• Understanding myocarditis in KD is crucial for comprehensive patient management and risk stratification.

Purpose of the Study:

• To characterize the histopathological features of myocarditis during the acute phase of Kawasaki disease.
• To determine the temporal evolution and spatial distribution of myocardial inflammation in KD patients.

Main Methods:

• Analysis of autopsy heart tissues from 29 patients deceased within 40 days of KD onset.
• Histopathological examination of myocardial interstitium across epicardial, middle, and endocardial layers at base, middle, and apex levels.
• Correlation of inflammatory cell infiltration patterns with disease duration.

Main Results:

• Myocarditis, characterized by lobulated leukocytes and large mononuclear cells, was present in all cases.
• Inflammatory cell infiltration was observed as early as disease day 6 and peaked by day 10.
• Inflammation was initially diffuse, later localizing to the epicardial layer at the base after day 10, and gradually subsided after day 20.

Conclusions:

• Myocarditis in Kawasaki disease precedes epicardial coronary arteritis and follows a distinct temporal pattern.
• The inflammation peaks around disease day 10 and resolves progressively after day 20.
• Myocardial inflammation distribution is heterogeneous, ranging from diffuse to localized epicardial involvement.