A 26-year-old woman, who suffered a seizure and became unresponsive during a Chinese therapeutic massage, had died from natural causes, an inquiry has found.

Ms Serene Lim Xin Hui was found to have died of interstitial pneumonia, a type of lung infection that can cause breathing difficulties and sudden death, even to persons at rest.

"The evidence points to no aspect of her treatment...including the massage performed on Ms Lim... having directly contributed to her death," said State Coroner Marvin Bay yesterday. He extended his condolences to her family, who did not attend the inquiry.

On Feb 14, Ms Lim had told her mother she was headed for a facial in Orchard Road. She went shopping and arrived at Qing Kang Integrated Chinese Medicine Clinic in Midpoint Orchard for a two-hour session of tuina, a Chinese therapeutic massage, around 5.30pm. Tuina is non-invasive and done on children as well.

Physician Ma Kejian, who examined Ms Lim, was told her body was sore and that she had diarrhoea. The court heard during the Coroner's Inquiry into her death that she had looked "pale" as well.

Reading Ms Lim's pulse, the physician assessed that she was well enough to undergo a massage.

The tuina session went ahead but around 7.25pm, when medical assistant Li Weiwei was about to massage her arm, Ms Lim's fists became tightly clenched.

"I thought she was stretching her back," said Ms Li, who was alone in the room with her. Ms Lim's body was also tense.

"When I saw that she was not moving, I called out to her."

But there was no response. The convulsions lasted about one to two minutes.

Ms Li rushed out to call for the physician and woman boss of the clinic.

They called emergency services and physician Ma, who was on his way back from another clinic.

He told them to massage the area between Ms Lim's thumb and forefinger, as well as above her upper lip - her acupoints. Ms Li also massaged one of Ms Lim's legs.

The Singapore Civil Defence Force guided them over the phone on how to perform resuscitation on Ms Lim, who was taken to Tan Tock Seng Hospital, where she was pronounced dead around 8.50pm.

The forensic pathologist who examined Ms Lim, Dr Chan Shijia, said interstitial pneumonia can cause a fever and general sense of feeling unwell. The most common cause of infection is viral, and this is generally confirmed by a blood test.

A physical examination by a general practitioner may yield evidence of a chest infection from abnormal lung sounds, she said. Most people eventually recover.

She found that Ms Lim was underweight, which could have made her more susceptible to infections, made recovery more difficult, and increased the risk of sudden death.

The symptoms of interstitial pneumonia can be quite varied, ranging from fever, body aches and coughs in more severe cases to non-specific symptoms such as lethargy, said Dr Chan. It is possible that someone exhibits no symptoms and subsequently dies from it, she said.

In response to queries, Dr Asok Kurup, an infectious diseases specialist based in Mount Elizabeth Hospital, said that while some infections could cause interstitial pneumonia, it is "very uncommon" for it to lead to sudden death.

While symptoms are not specific, having a cough with shortness of breath "may be a reason to be more alert", he added.

Such pneumonia may be linked with an inflammation of the heart muscles, leading to sudden death, but this is also not common, he said.