SINGAPORE – If there is one thing that Madam Chua Siew Tin, 49, regrets in life, it is passing on her defective gene to two of her four children.

The housewife found out that she has tuberous sclerosis complex (TSC) only after her eldest child, a daughter, was diagnosed in 2002 with the genetic disorder at around four months old after having fits.

The condition causes tumours to grow in various parts of the body. After Madam Chua was diagnosed with TSC, she was told that any child she has would have a 50 per cent chance of inheriting the disease.

Her third child, a son now 18, also has TSC. When he was two years old, he also had fits, each lasting about 15 minutes.

Madam Chua had not tested any of her children for the genetic defect after they were born, because of the cost. The blood sample has to be sent to the US and there is no subsidy or insurance to cover the roughly $1,000 needed for the procedure.

About half of the people with TSC have autism spectrum disorder.

Madam Chua’s son, who has tumours in his brain and kidneys, does not suffer from severe learning impairment, unlike her daughter, and is now in vocational training. But he lacks confidence as it takes him longer than his peers to learn something, so Madam Chua constantly encourages him.

Tumours in the brain can cause epileptic fits and significant cognitive impairment. Half of the patients with TSC have autism or learning disorders. Up to one in four has an IQ below 50 (most people score between 85 and 115).

Today, parents with TSC are advised to have children through in-vitro fertilisation and to undergo pre-implantation genetic testing – which became legal here in 2021 – to choose an embryo that does not carry the defect.

Speaking in Mandarin, Madam Chua said she blames herself for the suffering two of her children are going through, and is often very depressed. But she pulls herself together because she thinks that as it is her fault, she needs to be strong for her children.

Her own condition means she has had to be strong for herself too.

Before her TSC diagnosis, when she had health issues, doctors treated her without identifying the cause of the conditions.

In 1997, there was blood in her urine caused by her kidneys bleeding. This was treated at Singapore General Hospital, and she thought it was a one-off problem.

Three years later, her lungs collapsed and she was rushed to the National University Hospital.

She said the pain was terrible, like a huge weight was pressing down on her chest and face. Although she was breathing, she felt breathless as the oxygen was not going into her bloodstream.

The doctors in the emergency department punctured the surface of the pleural cavity to release the captured air. This allowed her lungs to expand and seal themselves. There are various causes for lung collapse, such as asthma, so again, she was discharged without knowing she had TSC.

Only later was it discovered that both her health scares were caused by TSC.

When Madam Chua’s first child was four months old and started having fits, she initially did not think much about the seizures, which were mild. She took her daughter to KK Women’s and Children’s Hospital (KKH) only when the fits became frequent and the child had a fever.

The doctors at KKH suspected the child had TSC and confirmed it with a blood test. That was when Madam Chua’s own condition was diagnosed.

Dr Loh Ne-Ron, a neurologist who runs the TSC clinic at KKH, said most parents do not recognise the spasms as seizures because they look like cartoon hiccups, when the arms are thrown forward and the body jerks.

Madam Chua’s daughter, now 22, has tumours in her brain, kidneys and skin, including her face. Her son, now 18, has tumours in his brain and kidneys. Like all women with TSC, her daughter has a one in 15 chance of suffering collapsed lungs.

She said her two children’s conditions and their need for care have put a strain on her marriage.

Their lifelong need for regular scans to monitor the tumours and their medication are costly, but she is able to manage with subsidies, insurance and MediFund, the government safety net to help people who cannot afford medical treatment.

But she is more optimistic now that her children are looked after by Dr Loh, who specialises in TSC, and there are drugs to treat TSC that were not yet on the market when her children were younger.

Two existing drugs were licensed for use in the US, in 2010 and 2013, to treat TSC as they are able to shrink the tumours. Everolimus is used to treat some cancers, while sirolimus is given to kidney transplant patients to prevent organ rejection.

Madam Chua said her children have a brighter future now.