In this study, we have shown decreased sulfation of CS in iPSECs derived from three genetically independent MMD patients with variant RNF213. Thus, in MMD, variant RNF213 causes changes in CS, and the endothelium becomes susceptible to shear stress, making it easier for EPCs to invade the vascular intima, where they would produce HA, resulting in intimal thickening and vascular stenosis. This evidence concerns the gene RNF213 and multiminicore myopathy.