Although high MMP-9 levels were expected in the UCRHTN subgroup, this negative findingmay be explained by the fact that all RHTN individuals have the hypertensive disease fora long time and take a great number of antihypertensive drugs, which could cause thedecrease in MMP-9 activity, particularly related to the use of ACE inhibitors, asevidenced by several studies21,22. This evidence concerns the gene MMP9 and hypertensive disorder.