Background: We report on 10 patients with Kawasaki disease and thrombocytopenia who were found to have a high incidence of coronary artery aneurysm and acute myocardial infarction. The clinical features of these patients, the cause of their thrombocytopenia and the relationship between cardiovascular pathology and thrombocytopenia were analyzed.
Methods: The clinical features of 10 patients with Kawasaki disease found to have thrombocytopenia (group A: mean age 8.0 +/- 7.0 months) and those of 293 patients with Kawasaki disease (group B, controls: mean age 13 +/- 20 months) were analyzed. Coagulation studies and bone marrow aspiration were performed to ascertain the cause of the thrombocytopenia in nine out of 10 subjects in group A.
Results: The minimum platelet count was 4-12 x 10(4)/mm3 (average day of illness, 10.3) and platelet counts were elevated to the baseline value within 1-2 weeks of onset of the illness. Low fibrinogen concentrations, high levels of fibrin degradation products, and low erythrocyte sedimentation rates with high C-reactive protein levels were observed in seven patients. In two other patients, immature megakaryocytes with normal coagulation values were observed. The differences in the incidence of coronary artery aneurysm and acute myocardial infarction between groups A and B were highly significant (coronary artery aneurysm: 60% in group A, 8.9% in group B; acute myocardial infarction: 40% in group A, 0.3% in group B).
Conclusions: In many patients with Kawasaki disease and thrombocytopenia, the thrombocytopenia appears to be a result of intravascular coagulation, and to be one of the risk factors for acute myocardial infarction.