We performed a ROC analysis and results showed that a serum MMP-9 level >1,011 ng/ml was associated with spontaneous hemorrhage in adult MMD patients with 70.37% sensitivity and 71.88% specificity (AUC 0.73, 95% CI 0.597–0.864, P = 0.003) (Figure 4). This evidence concerns the gene MMP9 and hemorrhage.