DNMT1 and purpura: In Henoch–Schoenlein Purpura, mitogen-activated protein kinase and extracellular signal-regulated kinase (MAPK/ERK) activity appears to be downregulated, resulting in less phosphorylated ERK, which is normally responsible for DNMT1 activation, thereby leading to reduced DNMT1 activity and potential epigenetic dysregulation contributing to the disease phenotype [100].