KUALA LUMPUR, MALAYSIA: He tilted his head from his mother's embrace and grinned upon hearing her voice.

For the past two years, these are the only movements Henry Wong is capable of.

Before this, the 8-year-old and his elder twin, Harry, were healthy. Like other kids their age, they loved to climb trees and ran everywhere.

But during their second year in kindergarten, the twins developed symptoms of Inborn Errors of Metabolism (IEM).

"Harry was very active in sports but he started to walk slowly and frequently tripped and fell. Suddenly, he couldn't talk," said his mother, Wong Yoke Leng, 47.

A month later, Henry developed the same symptoms.

"I was devastated as they were active and intelligent. It was very sudden."

IEM are rare diseases caused by parents' defective genes. Every year, 150 babies in Malaysia are born with IEM, which can be fatal if untreated.

Wong said she had a difficult time when the twins got the disease as she had to rush back from work to take them to see traditional healers.

"They told me my sons had monkey disease (according to Chinese belief), but I stopped going because of their ignorance.

"They refused to help because they didn't know what kind of sickness the boys had," said the single parent.

Wong eventually took the twins to the Kuala Lumpur Hospital and was told about the disease.

However, the exact type of IEM disease that they have has yet to be identified.

The twins go for a check-up every two months and stock up their medication. Wong said their medicine costs RM700 a month.

"Both of them take more than 50 pills a day, including vitamins, to prevent the disease from getting worse. I have to crush the vitamins and dilute them in water before feeding the boys."

The twins are on a strict diet of porridge, cereals and milk.

"Sometimes, they test my patience when they move a lot while eating. I've lost my temper a couple of times, but my mother always calms me down," said Wong.

Her mother, Chan Yoong, 71, lives with the family and is the only other person who is close to the boys. She bathes and feeds them when Wong has to go out on errands.

Wong is thankful that the Malaysian Metabolic Society is helping with money and moral support. During a charity dinner organised by the society, Wong received a donation of RM 400 for her twins.

The boys also received wheelchairs and get a monthly allowance of RM240 from the Welfare Department.