Patients diagnosed with Parkinson’s may actually have NIID, one study shows

A joint study by the National Neuroscience Institute (NNI) and the Singapore General Hospital (SGH) found that patients diagnosed with Parkinson’s may actually have NIID.

NIID is a disabling neurodegenerative disease due to a gene mutation and has no effective treatment. Symptoms of NIID include dementia, parkinsonism, balance disorders, and numbness and weakness in the limbs.

A patient with NIID may or may not have symptoms depending on their age and stage of the disease. The severe form of NIID usually occurs in elderly patients who have developed the disease.

The team studied more than 2,000 study participants, including healthy individuals and those with Parkinson’s disease (PD), for more than a decade.

They were surprised to find NIID-causing mutations in those diagnosed with PD. Dr. Ma Dongrui, Senior Medical Laboratory Scientist, Department of Neurology, SGH and lead author of the study, said, “To the best of our knowledge, this is the first study to report PD patients with NOTCH2NLC gene mutations in NIID patients.

Fortunately, they responded better to PD medication than most PD patients. This suggests that there must be factors that can influence why some develop PD while many others develop the more severe form of NIID.

When analyzing the NIID gene, the team found a group of healthy participants with a “milder” form of mutation. Such a mutation in the NIID gene could indicate that there is a risk of developing NIID or PD.

Because NIID can go undetected, a high index of suspicion may also be required in PD patients.

With what we now know, it might be beneficial for clinicians to look out for cognitive impairment or imaging clues early on that might suggest NIID in patients diagnosed with PD. Also, because NIID is caused by a genetic mutation, it may be worth looking for family members of PD patients who may show signs of NIID. „

Tan Eng King, professor, assistant medical director, and research director, National Neuroscience Institute

Our results suggest that many neurodegenerative diseases may overlap and share a common etiology. Finding a common link and uncovering the reason why a similar gene mutation leads to both mild Parkinson’s disease and a severe form of NIID can help identify new drugs for these diseases, “continues Prof. Tan who is also the lead author of the study and is a senior advisor at the NNI Department of Neurology on the SGH campus.

Following this study, the team plans to conduct more studies to better understand the mechanism behind NIID and identify new drugs for this condition.

Further research is needed to understand whether the broad clinical phenotype of NIID is related to the subtle genetic differences in the NOTCH2NLC locus, race, or other factors. Long-term follow-up of carriers of the gene mutation with a PD phenotype can provide additional information.

The study results were published online in JAMA Neurology am 24. August 2020.