Spinal Muscular Atrophy (SMA) is a genetic condition that causes progressive muscle degeneration and weakness, eventually leading to death.

SMA Type 1, which Caelen Lam has, presents itself in infancy, between three and six months of age, said Associate Professor Stacey Tay, who heads the paediatric neurology department at the National University Hospital.

It is the most severe out of the four sub-types. Each sub-type presents itself at a different age.

"Prognosis for SMA type 1 is poor and mortality is high," said Prof Tay.

There is no local data on SMA sufferers, but global data shows that about one in 80,000 suffers from SMA Type 1, she said.

Caelen's doctor, Dr Saumya Jamuar, said these patients cannot sit independently and their muscles weaken progressively.

A majority of these patients die before turning two years old due to respiratory insufficiency, the genetics consultant at KK Women's and Children's Hospital, added.

Both doctors, however, pointed out that some patients live beyond two years. "This could be related to more aggressive management or to other unidentified genetic modifiers," Dr Jamuar said.

Prof Tay said putting the children on respiratory support like non-invasive ventilation, which Caelen is on, or ventilation via tracheostomy, where a tube is inserted into the windpipe, "would change the natural history of the disease".

While there are patients here who have lived beyond two years old after tracheostomy, it is not recommended because of the "overall poor prognosis," she said.