Histological studies shed new light on the initiation and characteristics of calcification of coronary artery aneurysms in Kawasaki disease.

BACKGROUND: Calcification of coronary artery aneurysms (CAAs) is common in the remote phase of Kawasaki disease (KD), but the detailed features of its development remain unclear. This study aimed to elucidate the histological characteristics of calcification in KD CAAs.

MATERIALS AND METHODS: The study materials consisted of 24 coronary artery branches with aneurysms that were obtained from 14 Japanese patients who died during the period from 40 days to 3 years after the onset of KD. We first examined the CAAs for the presence of thrombi and calcification. When calcifications were observed, we determined their location and shape, and investigated the time-course of the changes based on the time-interval from KD onset until death. Then we measured the area of each calcification and examined for correlations between the calcified area, and (1) the disease duration, and (2) the aneurysm diameter.

RESULTS: Calcification was observed in 14 of 24 CAAs (in 7 of 13 LCA and 7 of 11 RCA). Thrombi were also seen in 13 of 14 CAAs with calcification. Calcification showed two localizations: in the organized portion of the thrombus (seen in 12 CAAs) and deep in the thickened tunica of the intima (3 CAAs). The earliest observation of calcification was in an infant who died on the 49th disease day: it was a small, band-shaped calcified lesion in granulation tissue that had formed at the boundary between the thrombus and the blood vessel wall. As the duration of KD increased, the calcified lesion increased in size, and nodular shapes were formed. Moreover, the calcified area tended to increase as the diameter of the aneurysm increased.

CONCLUSION: Histologically, CAA calcification starts early in the remote phase of KD, and it is closely related to organization of thrombi.