UC patients with active endoscopic disease at follow-up demonstrated significant lower proportions of PNAd+venules (4.0% (IQR 1.3–7.8%)) compared to their own baseline levels (5.3% (2.2–8.3%), p = 0.04), whereas an upregulation of MAdCAM-1 from baseline (5.5% (IQR 2.5–9.5%)) to follow-up (7.8% (IQR 4.5–12.0%), p = 0.001) was demonstrated. The gene discussed is MADCAM1; the disease is glycogen storage disease VI.