Peripheral blood eosinophilia and eosinophil accumulation in coronary microvessels in acute Kawasaki disease.

BACKGROUND: Early stage Kawasaki disease (KD) histopathology includes perivasculitis and vasculitis of the microvessels. The lesions then extend to larger vessels. Therefore the analysis of microvessel lesions is important to better understand the initial pathogenesis of KD vasculitis. METHODS AND
RESULTS: We studied epicardial microvessel lesions (<50 microm) and aneurysm lesions of paraffin-embedded cardiac tissues from 4 Japanese patients who died 7 to 22 days after KD onset. The cellular composition in the microvessel lesions was different from that in coronary aneurysm lesions; eosinophils were preferentially accumulated in the microvessel lesions. The average population of eosinophils was 16% of total infiltrated cells in the microvessel lesions, whereas it was 3% in the intima of aneurysm walls. We examined peripheral blood eosinophil cell counts in 95 KD patients and 95 febrile age-matched controls. Baseline eosinophil cell counts in KD patients were higher than those in febrile control patients (361 +/- 441 65 +/- 133; < 0.0001). Eosinophilia (>350 cells/microl) before therapy was documented in 36% of KD patients, but in only 4% of febrile controls ( < 0.0001). Sixty-six KD patients (69%) developed eosinophilia within 2 weeks of illness.
CONCLUSIONS: Because the numbers of circulating eosinophils in the body are tightly regulated, eosinophil accumulation in blood or tissues may reflect the host's immune response against KD related antigen(s).