Three teams of scientists have identified a genetic mutation that is linked to about 5 percent of inherited cases of Parkinson’s disease.

The fault on the recently discovered LRRK2 gene is one of five genetic defects linked to the progressive nervous system disorder and could lead to improved diagnosis and the development of a genetic test.

“Our results suggest that the mutation we have studied is the most common cause of Parkinson’s disease identified to date,” said Dr Tatiana Foroud, an associate professor at Indiana University School of Medicine in Indianapolis.

The research is one of three studies by scientists in Britain, the Netherlands and the United States who identified the LRRK2 gene mutation. Their findings are published online by The Lancet medical journal Tuesday.

Foroud and her colleagues pinpointed the defect by analyzing the genetic background of 767 Parkinson’s disease patients from 358 different families.

Dr Nicholas Wood, of the National Hospital for Neurology and Neurosurgery in London, and his team focused on patients without a family history of the illness. They found it was also implicated in sporadic cases.

Dr Vincenzo Bonifati of Erasmus Medical Center in Rotterdam in the Netherlands studied 61 families with two or more members with the illness.

“We found there is a novel mutation which is common in these families,” Bonifati said in an interview. “The other groups in the UK and the US found the same mutation independently.”

Parkinson’s is a chronic, irreversible neurodegenerative disease that affects 1 percent of people over the age of 65 worldwide. Actor Michael J Fox and boxing legend Mohammed Ali are sufferers.

The illness occurs when brain cells that produce a chemical called dopamine malfunction and die. Symptoms include tremors, stiffness, slow movement and poor coordination and balance.

“It is very important for scientists to establish novel (therapeutic) approaches based on the function of this gene,” said Bonifati.

“The main challenge is now to try and understand how this and other Parkinson disease-associated LRRK2 mutations lead to neurodegenerative disease, in order to design novel therapeutic and preventive strategies,” he added.

SOURCE: Lancet, online January 18, 2005.