HLA-DRA and Parkinson disease: Future studies are warranted to elucidate their roles in the pathophysiology of PD and potential association between AS accumulation in the myenteric plexus of the colon and significantly identified genes such as LAMP1, TUBB2A, and S100B in the myenteric plexus, and HLA-DRA, SERPINA1, and metallothioneins in the intestinal epithelium.