Teen swimmer overcomes rare PTPS deficiency

“Serotonin governs mood, sleep and emotional well-being, so low levels can lead to behavioural and cognitive difficulties,” the geneticist said.

“In short, it simultaneously starves the brain of two neurotransmitters, which is what makes it so serious if left untreated.”

The condition is “ultra-rare”, affecting approximately one in a million people worldwide, though its prevalence varies significantly by ethnicity and region.

Yeo said the condition is noticeably more common in Asian populations than in Caucasian populations. Currently, there are only three known cases in Singapore, including Jessica.

Early detection gives her a better chance at a normal life

Due to her BH4 deficiency, Jessica’s newborn screening detected an excessive amount of phenylalanine, an essential amino acid that is usually found in foods such as meat, fish, eggs, dairy and beans.

Doctors were able to treat her early. Left untreated, the condition could have left Jessica intellectually disabled, with severe developmental delays, and caused seizures.

“Delayed treatment could also result in dystonia, a neurological movement disorder causing muscles to contract involuntarily, leading to twisting movements or abnormal postures,” Yeo said.

“There is no cure for PTPS deficiency, and Jessica’s treatment generally focuses on reducing high levels of phenylalanine and replacing dopamine and serotonin,” she added.

Her low levels of dopamine and serotonin also contributed to her disrupted sleep patterns.

Jessica told ST: “I often fell asleep in class in primary school, especially during Chinese class. My teachers were told of my condition, so there was no issue, nor was I scolded.”

Despite starting medication early, Jessica developed seizures when she turned 10.

She was put on synthetic BH4 to help lower her blood phenylalanine levels. The medication acts as a cofactor, or helper molecule, for multiple enzymes in the body, including the enzyme in the liver responsible for processing phenylalanine.

Yeo said: “But synthetic BH4 alone cannot fix Jessica’s neurotransmitter deficits in the brain. To restore her dopamine levels, she is prescribed levodopa; and for serotonin, she is given 5-hydroxytryptophan to allow the brain to successfully manufacture serotonin.” ‎

Jessica’s medication costs thousands of dollars a month and the expense is lifelong, with her medical bill increasing as she grows older.

“We are not rich. My father is a mechanic and my mother a swimming coach,” Jessica said.

The family is financially supported by the Rare Disease Fund, which covers a large portion of her treatment costs.

Jessica, who found out about her condition only when she was 13, added: “I need to take six pills and capsules every morning, two in the afternoon and three at night just to keep my symptoms at bay.”

And kept it at bay the medications did. The seizures, which started when she was 10, went away in 2023.

Despite her low muscle tone, Jessica continues to swim competitively, some days under her mother’s watchful eye.

She wants to graduate and work as an engineer and “perhaps teach coding in a robotics school one day”.

Despite her condition and the bullying she experienced in primary and secondary school while growing up, Jessica continues to have a happy outlook on life.

“We should accept our flaws, even when others look down at us for them. Never be discouraged,” she said.