The study, conducted by Dr William Nichols, a geneticist at Cincinnati Children’s Hospital Medical Center, has been published in the medical journal The Lancet, as well as studies by Dr Nicholas Wood of the Institute of Neurology in London and Dr Vincenzo Bonifati of Erasmus MC in Rotterdam, Netherlands.
The Cincinnati Children’s study focused on a group of 767 Parkinson’s disease patients from 358 different families. The study found that 5% of the patients carried the same LRRK2 mutation.
The Wood report focused on Parkinson’s disease patients without a known family history of the disease and found the same LRRK2 gene mutation in eight of 482 individuals in the study.
The Bonifati study identified the same LRRK2 gene mutation as the Cincinnati Children’s study. Bonifati found the mutation in four of 61 families with a history of Parkinson’s disease.
“When we began, we really didn’t know how frequent the mutation in the LRRK2 gene would be, but to find the same single mutation in the genome in Parkinson’s patients is pretty dramatic. No other mutation in any other known Parkinson’s gene has been found in such high frequency,” said Dr Nichols.
Individual genes can have many mutations, which is also true of the LRRK2 gene. Other mutations in the LRRK2 gene have been identified, but those mutations were not manifested to the same degree as the mutation described in Nichols’ study, which was found to occur in about one of every 22 patients with inherited Parkinson’s disease.
“Finding the same mutation in a single gene accounting for such a large percentage of patients is quite remarkable, and this mutation should be included in any future genetic testing for the disease,” Dr Nichols said.
Until recently, it was thought that environmental factors were the primary cause of Parkinson’s disease. A genetic link was thought to exist in the rare early onset form of the disease in people diagnosed before age 40, but not in the more common form of the disease in which people, on average, are diagnosed at about 60 years. The first Parkinson’s disease gene was identified in 1997.