The disease that left Cheng Kwan-yee paralysed since birth was finally identified when she was 17. Due to her illness, the teenager, now 18 years old, has never talked, walked, fed herself or performed the most routine of daily activities on her own.
Her family had waited three years for a diagnosis.
During that time, doctors sent her tissue samples overseas - the tests were still not available in Hong Kong - as they tried to determine whether she had mitochondrial disease - a rare group of neurometabolic diseases.
The mystery was solved when the diagnosis was confirmed, but it provided little relief as there is still no cure for the disease. Kwan-yee's mother, Manda Hong Po-kei, believes her condition could have been better managed if the disease had been identified earlier.
Other sufferers may be luckier. Thanks to medical advances and doctors' efforts, patients with the disease are about to see a change for the better.
After years of appeals for donations, equipment to diagnose the ailment was brought to Hong Kong a few months ago and will be operational at the Queen Mary Hospital next year, after a trial.
"The most painful times have passed, we're on a much brighter road now," said Dr Fung Cheuk-wing, paediatrics associate consultant at the Duchess of Kent Children's Hospital.
Fung has a special interest in neurometabolic diseases, including mitochondrial disease. For almost five years, his team has been fighting for a HK$1 million donation to bring the diagnostic facilities to Hong Kong.
Fung is still seeking donations to fund the training of staff to run the service.
So far, cases of mitochondrial diseases in Hong Kong remain rare. Since the hospital began a specialised outpatient neurometabolic service in 2009, a few cases have been found, but 38 other suspected cases are still waiting for a diagnosis. More are expected to be identified.
At the moment, diagnosis only means that patients' symptoms - such as strokes, muscle weakness or bad co-ordination - may be relieved by medication, as there is no cure for most mitochondrial diseases.
But Fung believes diagnosis can offer more than that.
In recent years, more treatment strategies have been developed around the world for diseases that were previously thought to be untreatable.
"We have an urgent need for suspected cases to be diagnosed now, to have them prepared [for] when new drugs come into the market," he said. "We must not take them as untreatable diseases, we must have hope."
Kwan-yee was misdiagnosed as suffering from cerebral palsy when she was one year old.
Like cerebral palsy patients, she cannot control her muscles. They are sometimes so tense that she is in too much pain to sleep.
It wasn't until she was 14 that Fung came across her case and suspected that her condition was, in fact, caused by mitochondrial disease.
While the delay did not cause Kwan-yee to miss out on early treatment - as none was available - for other patients with different types of mitochondrial disease, that could have been the case, said Fung.
Understanding of neurometabolic diseases only began gathering pace in the past decade. New diseases that fall under this category are still being discovered every one to two years.
Fung hopes for more doctors in Hong Kong to become aware of the disease so that they can flag suspected cases.
Treatments have been found for some neurometabolic diseases in recent years, sometimes with dramatic results. Previously paralysed and lifeless patients have been able to walk and talk after treatment.
Now with the diagnostic equipment, Fung's team has started a pilot programme for the diagnosis and management of mitochondrial diseases. He hopes that a pattern, specific to Chinese, in the genetic causes of mitochondrial diseases can be discovered in the next three to five years.
He would also like the programme to move to the government's proposed Centre of Excellence in Paediatrics in future.
As for Kwan-yee, the only thing that can ease her condition at the moment are drugs to lessen her symptoms and a special formula milk which may help relieve her muscle problems.
"I have faith that in the future there will be drugs for Kwan-yee and the others. Meanwhile, I hope these poor patients can wait," said Fung.
Kwan-yee's mother's wish is small: "If she could at least become capable of expressing herself - letting me know when she is hungry or when she needs to go to the toilet, I will be very grateful."