Furthermore, increased expression of MMP9 and TIMP-1 and significantly increased serum levels of MMP9 and TIMP-1 were observed in myocardial biopsy samples compared with those of patients with ATTR amyloidosis with the same level of left ventricular hypertrophy [64], suggesting significant activation of extracellular matrix proteolysis in AL cardiomyopathy [55]. The gene discussed is MMP9; the disease is left ventricular hypertrophy.