Multiple studies’ pooled data revealed a significantly increased risk of Parkinson’s when combined with bullous pemphigoid, a rare skin condition, inflammatory bowel disease (IBD), or Sjögren’s syndrome. Immune response impairment has been linked to Parkinson’s disease in a growing body of evidence. Indeed, some studies have suggested that the neurodegenerative disease may be exacerbated by autoimmune processes, which occur when the immune system incorrectly attacks and destroys healthy tissue.