With every hospital visit for his daughter Chloe's medical treatment, Mr Kenneth Mah chalks up a bill of more than $10,000.
Each weekly dose of medicine is just half a gram of powder mixed with water, which is then given to the eight-year-old through an intravenous drip.
The bulk of Chloe's medical bills, which easily hit $40,000 a month, goes towards paying for the drug, called Myozyme - the only known treatment for the rare ailment that Chloe suffers from.
Known as Pompe disease, it is a genetic disorder caused by the lack of a certain enzyme. As a result, Chloe's muscles are weak and she needs help to breathe and cough.
There is no cure for the disease, which is often fatal. To stay alive, Chloe needs to be on the medication her whole life.
There are no official numbers on how many people in Singapore have such rare diseases.
Like many other parents in his shoes, Mr Mah knows of fewer than five people here with Chloe's condition. And similar to her case, the drugs to treat and manage such rare diseases can be very costly for a patient's family.
The Mah family are fortunate as insurance covers much of the costs involved. But other patients may not be as lucky if they do not have similar insurance coverage or qualify for government subsidies.
For instance, as such diseases often show up at birth or early in childhood, parents may not have been able to buy insurance for them. Insurers may also not provide coverage for such congenital conditions.
Under Singapore law, rare diseases refer to illnesses that are "life-threatening and severely debilitating", and which affect fewer than 20,000 people. But the sheer variety of rare diseases - there are more than 7,000 different kinds - means that their cumulative impact on Singapore may not be small.
Mr R. Rajakanth, executive director of patient advocacy group Rainbow Across Borders, estimates that there could be 2,000 to 3,000 rare disease patients in Singapore.
Earlier this year, the group published a study of the impact that such diseases have on families. It found that such ailments can take a heavy financial and emotional toll.
"It is often a lonely journey for the patients and their caregivers," said Dr Tan Ee Shien, a senior consultant with the genetic service at KK Women's and Children's Hospital's paediatrics department.
"Often, there can be only one or two families in Singapore with that condition. With a lack of awareness, there is less empathy."
The problems start at diagnosis, which can take years. Some patients never get a confirmed diagnosis at all.
"This is an issue because there's so much uncertainty about the next steps," Mr Rajakanth said.
Even among those who know what they are up against, the odds are stacked against them.
In eight out of 10 cases, there is no medication available to treat the underlying condition, said Associate Professor Denise Goh, who heads the paediatric genetics and metabolism division at the National University Hospital (NUH).
"We treat the symptoms to either slow down or reduce the effect (of the disease) on the patients and their families," said Prof Goh, who estimated that NUH sees between 100 and 200 such patients every year.
And for the minority of patients for whom treatment is available, the costs of medication can be astronomical - as in Chloe's case.
Apart from the financial burden, families also have to deal with the emotional and social demands of caring for such children.
"Parents can face a lot of guilt and blame because it's often related to genetics," said Mr Rajakanth, who has heard of incidents where spouses blame each other for a child's health problems, or are blamed by their in-laws.
Mr Mah, who is co-founder of the Rare Disorders Society Singapore, said he has also been told of cases where well-meaning strangers tell parents: "Don't worry, your next child will be normal."
Mr Mah and his wife, along with Chloe and their younger son Cayden, aged five, live in a condominium with Mr Mah's parents. Mr Mah quit his job to be a full-time caregiver, while his wife works in the insurance industry. The family's monthly household income is about $7,000.
Mr Mah and his sister bought the condominium apartment more than a decade before Chloe was born.
Although Chloe's hospital treatment is fully covered by insurance, the family pays around $300 in cash every month for the other things that she needs, such as gauze pads and gloves. They have also had to make more expensive one-off purchases to help her, such as a specialised wheelchair, ventilator and machine to help her cough.
For patients who cannot get government assistance and insurance coverage, or if either of these is not enough, Mr Mah said that pharmaceutical companies sometimes pay for the treatment.
But as Chloe grows older and requires more of the drug to stay alive, she will likely hit the yearly insurance claim limit at some point.
Mr Mah said that he has no fixed plans for that eventuality, although he hopes that a cure will be invented in the years to come.
He said: "We just live day to day. We dare not look too far ahead."