Rare ZTTK syndrome: Singapore boy’s genetic condition explained

Goh said the possibility of the condition being missed, misdiagnosed or even undiagnosed is high because ZTTK syndrome is very rare and its symptoms overlap with other neurological conditions.

Genetic counsellor Priscella Chia from KKH, who also attends to Teyden, said it is “entirely normal for the first few tests to come back inconclusive”.

“About 80 per cent of rare diseases present with vague, overlapping symptoms. Standard medical tests (like basic blood work or imaging) usually rule out common conditions rather than pinpoint a rare one,” she added.

Woo said it was an emotional roller coaster for her and her husband when Teyden was diagnosed.

“I felt sad that I was the one who gave him his condition. At the same time, we were happy that we finally had a diagnosis for Teyden’s condition. We also had a lot of help from his physiotherapists, who have taught us how to manage him,” she said.

“It helps also that Teyden is a super happy child, and it makes it easy for us to take care of him.”

Teyden now attends physiotherapy twice a week to work on his posture, trunk control and overall motor function at the Wings Therapy and Learning Centre in Singapore.

“We started intensive sessions in June, and it helped him a lot. Now he is able to sit up on his own for a period of time, which he could not do before. He was really floppy, and his head control was very weak,” Woo said.

Teyden also tends to shake his arms and move his head to hit the back of his high chair, a known neurological manifestation of ZTTK syndrome associated with several central nervous system anomalies.

“He cries when we stop him. To prevent him from hurting himself, we have put a cushion behind him. (But) he seems to know it is soft, so he goes at it harder. He is cheeky that way,” Woo said.

The seizures start

At the end of May, Teyden started having seizures, a symptom that affects between 50 per cent and 55 per cent of ZTTK syndrome patients.

“We did not know they were seizures. He was still on the BiPAP. He was still asleep, jerking. There was foam coming from his mouth, and he was slowly turning blue. We called the ambulance,” Woo said.

A BiPAP machine is a non-invasive ventilator used to help with breathing by delivering pressurised air through a mask: higher pressure for inhalation and lower pressure for exhalation.

When Teyden had another seizure weeks later, his parents were ready with the video camera, and they managed to capture the 11-minute incident and report it to the attending doctor at the emergency room in KKH.

Teyden is on anti-seizure medication, but he still experienced another episode – this time brought on by fever and Covid-19. This meant he could have faced a significantly higher risk of severe symptoms or respiratory complications.

“It was the scariest point of the two years of his life,” his mother said.

Having recovered, Teyden is back to playing with the two family pets and attending classes at Fei Yue EIPIC Centre in Upper Thomson Road, which offers an early intervention programme for young children with developmental and special needs.

“He is the youngest there, and the loudest in class,” Woo said, laughing.

Teyden’s father Ho Jun Han, 27, a data centre operator, said the boy likes to be involved in conversations and babbles a lot, even though he cannot form words.

They have joined a Facebook support group that is based in the US.

“Apart from Teyden, there is no one else in Singapore with his condition. It was here on this Facebook page that we got to see other kids with ZTTK, contact parents dealing with the condition and perhaps provide support for each other,” Woo said.

“We do not know what the future holds for him because this condition is super rare… We are managing and trying to stay as positive as much as possible.”