MMP9 and myeloid sarcoma: Previous studies on recombinant interferon beta-1a, one of the most used disease-modifying therapies for MS, showed that low MMP-9 serum levels were associated with a positive outcome, while MMP-2 serum levels were stable during treatment [36] and that serum MMP-9/TIMP-1 ratio may be regarded as a reliable marker and may be predictive of MRI activity in RRMS [37].