The presence of glomerulonephritis (GN) had a statistically significant effect on the reduction of MMP-2 levels both in patients treated with β-blockers [139.8 (117.6–142.8) vs. 192.3 (161.4–237.6) ng/mL, p = 0.044] and in patients not taking β-blockers [217.4 (159.0–276.6) vs. 259.2 (226.2–318.6) ng/mL, p = 0.036]. The gene discussed is MMP2; the disease is ganglioneuroma.