Parkinson's disease pathogenesis, evolution and alternative pathways: A review.

Sporadic Parkinson's disease (PD) is one of the most common neurodegenerative diseases of the elderly. In the scientific literature, surveys aiming to investigate the potential diagnostic biomarkers for PD have focused on skin and intestinal tissue biopsies, whereas more recent studies have reported an association between PD and skin disorders, such as seborrheic dermatitis and rosacea. In addition, a connection between PD and Crohn's disease has been established. These data suggest the hypothesis of a possible link between the gastrointestinal tract and skin and the development of PD. In fact, the nervous system, gastrointestinal tract and skin are analogous in their embryological development and, therefore, have molecular networks and pathogenic pathways in common. Based on these data, it may be assumed that the gastrointestinal tract and skin might be implicated in the pathogenesis of PD. The evolutionary hypothesis might also be a useful tool for further investigations into the overlap across neurological, gastrointestinal and skin disorders.