Parkinson's and Crohn's Disease: What's the Connection?

New research shows a genetic correlation between Parkinson's disease (PD) and Crohn's, two diseases with no known cause or cure. A possible genetic link is related to mutations in the LRRK2 gene (pronounced "Lark-2"). The LRRK2 association with Parkinson's has been under investigation for years. Researchers at The Mount Sinai School of Medicine in New York have recently identified variations in LRRK2 that may contribute to the risk of developing Crohn's disease.¹

What is Parkinson's disease?

Parkinson's is a chronic neurodegenerative motor disorder that is characterized by difficulty with movement. LRRK2 has been associated with the development of Parkinson's disease, and it is more common in Ashkenazi Jewish PD population (15-20%) than in the general population (1-2%).²

What is Crohn's disease?

Crohn's disease is a chronic inflammatory condition that affects the digestive tract. It falls into the category of inflammatory bowel disease (IBD). A combination of genetic predisposition, presence of microorganisms like bacteria, yeast and viruses, as well as environmental factors, can contribute to the development of Crohn's.

Crohn's can impact anywhere in the GI tract but most often affects a portion of the small intestine (ileum). People who have Crohn's may experience abdominal pain, weight loss and diarrhea as well as bloody stool or other rectal bleeding. As it is an inflammatory condition, there can also be additional affects on joints. It's thought that the immune system overreacts to microorganisms in the digestive tract, and environmental factors may trigger that overreaction.³

Research studies have sought to identify the genome association to better understand why Crohn's is more likely to develop in certain people, such as the Ashkenazi Jewish population.⁴ Genomes are the complete set of genetic material in a cell or organism. They represent all the parts and all the instructions for how an organism should grow.

The link between Crohn's and Parkinson's

Two newly recognized LRRK2 gene variations were found to impact both PD and Crohn's. The biology underlying these mutations will be an area rich for additional scientific study to investigate and possibly predict who might be at greater risk for developing these conditions.

Crohn's has genetic and environmental factors that contribute to the onset of the disease. Earlier studies looked at over 5,000 people from Ashkenazi Jewish descent, more than 2,000 of who had Crohn's. Two gene mutations were identified. One had a protective effect and one a contributory effect. Looking at nearly 25,000 people, the findings indicated that those who had Crohn's had a higher likelihood of the risk mutation and those without the disease more often had the protective mutation.¹ The same set of mutations and associated risks were evident in Parkinson's patients. Further, these findings held up regardless of ethnic background.

According to lead author Dr. Inga Peter, functional variants in the LRRK2 gene confer shared effects on risk for Crohn's disease and Parkinson's disease.¹ It seems that one gene can affect multiple traits. Genetics and genomic research sought to investigate what factors contribute to disease development in populations that are more susceptible to developing the diseases.

Impact on treatment

Parkinson's and Crohn's are both traditionally treated with drug therapy. The selection and use of available medications varies based on severity, disease stage, and other conditions that an individual may have. New innovations in research have boosted the field of personalized medicine; an approach to medical care that is customized for each patient. As personalized medicine continues to develop, understanding the biological mechanisms of disease can help to identify and refine appropriate treatments. Customized therapies that address the variations caused by LRRK2 mutations may be useful in the future to the general Parkinson's population.²

Dr. Judy Cho, co-author and director of the Institute for Personalized Medicine at the Icahn School of Medicine at Mount Sinai, explained that defining the biology of naturally occurring protective mutations is important because they can influence the direction for developing potentially new therapies needed to better treat the disease.