For the first year of her life, a baby girl fought multiple infections that left doctors at KK Women's and Children's Hospital (KKH) puzzled because they could not diagnose the root cause of her problems.

Rashes would break out on the infant's skin, there was a huge ulcer on her buttocks that needed to be drained, and there was milky fluid in her lungs. When one problem was treated, another would surface.

For nine months, doctors put her through various tests, with no success. That was, until they checked her genomic make-up with a new rapid sequencing test developed in-house by KKH doctors.

They found that her immune function was compromised. They did a total bone marrow transplant and the girl was able to go home. She had about a year of normal life before her body rejected the transplanted stem cells.

She died at the age of 2½. She is only one of four known cases in the world with this genetic disorder.

Dr Saumya Shekhar Jamuar, a senior consultant specialising in genetics in children, said the girl and her family had at least a year of normal life, without the suffering she experienced in her first year of life.

The KKH genetics team developed the test to provide faster diagnosis of rare diseases. They have sequenced 380 children since 2014 and were able to diagnose the problem for two in five of them.

They now plan to use the sequencing initially on about 50 children a year who are in intensive care, where doctors have difficulty diagnosing the problem. It can also be used on another 200 to 250 people a year whose ailments are proving hard to pin down.

Under this test, blood is taken from the child and the DNA is sequenced. The variants are identified and compared with ethnic-specific reference points to see what is unique about the child that could be responsible for the illness.

In some cases, after the cause was identified, the doctors changed the way they were managing the children. In others, it did not make much difference except to let the family know exactly what was wrong.

A couple had two children born with underdeveloped brains who had died shortly after birth.

The doctors identified the culprit gene and informed the couple that there was a 25 per cent chance of the same issue occurring in future pregnancies. The couple have now opted for in-vitro fertilisation so the embryos can be tested for this gene before the implant.

In some cases, even when no cure is available, the parents have "closure" in finding out what is wrong with their child.

Madam Serene Poh, knew something was wrong when her son Jayden Tan was late holding up his head, and could not even crawl when he was 1½ years old. He could not talk either and had difficulty swallowing.

The gene test identified his problem as Pura syndrome. Now 12, he is the only person here known to have this problem. There is no cure, but his mother said she has been able to get in touch with families of other patients around the world.

The oldest survivor with Pura syndrome is a 28-year-old woman, which gives Madam Poh hope that Jayden can have a future. He is the second of her four children.

He underwent physio-, occupational and speech therapies at KKH and can now walk unaided for about 200m. He still doesn't talk, but understands what is said.

KKH is not the first to do such genetic sequencing. But the doctors said one advantage of developing it locally is getting an Asian gene pool, which might be different from Caucasians'. The test costs the hospital $3,600 to $6,000. Overseas, it is priced at $8,000.