Parkinson’s disease is the world’s fastest-growing neurological disease. In Part II of her series on the degenerative brain condition, Donna Chisholm writes about the genetic fault that can trigger Parkinson’s in young Western Polynesians, and the NZ researchers who are determined to find a cure. To read Part I, go here.
New Zealanders diagnosed with Parkinson’s are, on average, 59 years old. When doctors confirmed Sia’s (not her real name) diagnosis last September, she was just 29. She noticed her first symptoms – gait and balance issues – after the birth of her second child in 2016. She has kept her diagnosis secret from friends and wider family as she comes to terms with her new future. In particular, she doesn’t want her mother – diagnosed with the disease at 36 and now severely unwell – to find out and blame herself. “It would break her heart.”
Sia and her mother, who are Samoan, are in a small minority of Parkinson’s patients whose condition is purely genetic. They have each inherited two faulty copies of the PINK1 gene. Sia got one from her mother but the faulty gene is so common in people whose ancestors are from western Polynesia – it’s estimated 1 in 18 people from this region carry one copy – that her father by bad luck must have been a carrier too. There are estimated to be hundreds of cases in the Pacific and, through migration, New Zealand.
The PINK1 gene was identified 20 years ago as a cause of Parkinson’s disease but is rare around the world. In 2018, Auckland neurologists tested the first two young Pacific people – one from Samoa and one from Tonga – and discovered they both had the double dose of faulty PINK1 genes. They had noticed there was a group of young Polynesians with Parkinson’s and this seemed likely to be the cause.
Study co-ordinator Dr Christina Buchanan is trying to determine the prevalence of the mutation here. In the past four years, her Neurological Foundation-funded studies have gene-tested 39 people with young-onset Parkinson’s, 35 of whom were from the Pacific. Of those, 27 had the double PINK1 mutation. One patient diagnosed in his late 20s had symptoms from age 12. Buchanan and her team have just received a $174,000 Health Research Council grant for a longitudinal study to learn more about the course of the disease.
Her colleague Associate Professor Richard Roxburgh, the neurologist who arranged genetic tests for the first Tongan patient diagnosed here, says having a clear genetic cause allows the prospect of a targeted treatment. His team have already developed a mouse model of PINK1 to better understand the process that causes Parkinson’s and to test possible therapies. He believes that because we know exactly what causes genetic forms of Parkinson’s disease there is real hope for a cure, though clinical trials could be 5-10 years away.
For Sia, an Auckland warehouse manager, the first sign something was wrong came when she had trouble holding herself up – she would fall forward on to the bed when changing her son’s nappies. Then her family noticed she was “waddling” when she walked, listing towards her left side. Although she saw a neurologist at the time, and early Parkinson’s was suspected, she was thought to be too young and was told to return if her symptoms worsened.
They did, after a particularly stressful period following her grandmother’s death in 2022. After returning home from the headstone unveiling in 2023, she fell down face-first three times, unable to save herself in a “severe freeze”. She also noticed her writing was getting smaller.
Dutch Parkinson’s expert Professor Bas Bloem says many people with the condition say their symptoms emerged at a time of high stress, and he’s recently co-authored a paper on the phenomenon, titled “The Last Straw”.
“We know that stress consumes dopamine, and if you have Parkinson’s, stress makes the symptoms temporarily worse. If you are on the brink of developing Parkinson’s and have a stressful event, it might be why you topple over the edge. The stress goes away, but the Parkinson’s doesn’t.”
Sia’s diagnosis, confirmed by gene tests, led to a period of deep depression. Her biggest fear is a loss of independence and one day being no longer able to drive. “I felt like that was my end. I took it as a full stop, that nothing else was going to get better for me. Then I looked at my kids and thought I can’t be like that.”
She’s since joined a support group for other Pacific sufferers and is working hard to change her outlook, particularly while her symptoms are well controlled by medication. “It’s a lonely condition. But I thought you can either keep your head in the sand or get up and do something about it. I felt if I’m going to take two years to come to terms with it, what am I going to achieve in that time? I’m the type to get shit done.
“Most Parkinson’s people think they’re broken. But being broken is saying you can’t be repaired … if you put the pieces back together, you see the cracks, but just see them as scars from the battle. Things that are broken can be fixed.”
