Up to 12 people drop dead every year in New Zealand from a heart condition called Long QT syndrome.
The New Zealand researcher who discovered the condition says it's probably the most common cause of young sudden death in the country, but it is manageable.
In one Auckland family, the mother and all three daughters have the condition.
Youngest daughter Teina Maoate looks like any other 10-year-old going for a run, but when you look closer, you can see when she exercises one half of her face isn't like the other.
"I had an operation called a sympathectomy and a side effect is me having a half-red face and a half-non-red face," she told Newshub.
Teina had the surgery for a rare heart condition known as Long QT Syndrome.
Cutting a nerve connected to the heart reduces risk of cardiac arrest by 60 percent, but splits the body down the middle so that one half won't sweat, blush or react to the cold as much.
Her two older sisters Ruby and Georgia have also had the surgery.
It's almost been four years since Georgia collapsed after going up and down a staircase. The collapse prompted a visit to the doctor - and less than a fortnight later, all three daughters and their mother found out they had Long QT Syndrome.
With Long QT Syndrome, the time between the Q and the T waves - when the heart is recharging - is longer than normal, affecting the T wave.
Even though 15-year-old Ruby had the nerve surgery, she collapsed at school during a PE lesson in 2017, leaving her mother Mandy Maoate terrified.
"It was hideous... It's every parent's nightmare," she said.
As a result, Ruby had an internal cardiac defibrillator (ICD) inserted under her armpit.
"Because it's tucked under some muscles... I can play sports and live my life as I would," Ruby told Newshub.
It collects information about her heart, which she syncs each week and sends to the US. If there are any issues, her specialist at Starship Hospital is contacted.
Older sister Georgia is trying to make her life a little bit easier.
"I'm making a sports bra for my sister in textiles that has some built in protection for her ICD so she can play sports and know that she's protected," she told Newshub.
Learning they have Long QT has shone a new light on some old family mysteries.
"This family seems to have quite a nasty version of this with the sudden deaths through the family," said cardiologist Dr Jon Skinner, who continues to search for a cure.
The condition was found in the 1970s but the genetic condition was not found until the 1990s, he said.
"My father died at 39, suddenly, and his brother died suddenly at 10 and his sister died suddenly at 21," Ms Maoate said.
There are 550 people known to be living with Long QT in New Zealand - and at least four of them are managing it brilliantly.