MMP2 and Achalasia: When comparing data from the combined two cohorts of achalasia patients (n = 88) with matched controls (n = 60), we observed that the total levels of MMP-9 (Fig. 1b) were similar in achalasia and controls, whereas the levels of the MMP-9 monomer (Fig. 1e) and MMP-2 levels (Fig. 1c) were significantly altered in achalasia versus control.