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MERRF syndrome is a rare genetic disorder that primarily affects the nervous system and muscles.

Medical Mysteries

Medical Mysteries is a series that spotlights rare diseases or unusual conditions.

Nanyang Academy of Fine Arts student Abigail Chua, 20, inherited her rare genetic condition from her mother.

ST PHOTO: JASON QUAH

Published Apr 11, 2026, 12:00 PM

Updated Apr 11, 2026, 12:00 PM

SINGAPORE – The swelling in her legs persisted for over a week, so Abigail Chua, then 13, went to the doctor and was put through a battery of tests to get to its root cause.

After two weeks of scans and tests, she was diagnosed with Myoclonic Epilepsy with Ragged-Red Fibres (MERRF) syndrome, a rare genetic disorder that primarily affects the nervous system and muscles.

“It affects the mitochondria or ‘power plants’ of our cells, robbing the body of the energy it needs to function properly, particularly in energy-hungry organs like the brain and muscles,” Dr Koh Ai Ling, a consultant with the Department of Genomic Medicine at KK Women’s and Children’s Hospital (KKH), told The Straits Times.

She added that the name of the condition comes from two of its “hallmark features”: myoclonic epilepsy which results in sudden, involuntary muscle twitches or seizures; and ragged-red fibres, the abnormal clumps of mitochondria that look like red, tattered threads when viewed under a microscope.

While the exact number of people with MERRF syndrome is “hard to pin down because it is often underdiagnosed”, medical literature suggests it affects fewer than one in 100,000 people worldwide.

“It remains a ‘needle in a haystack’ diagnosis for most clinicians,” Dr Koh said.

Dr Koh said MERRF syndrome happens because of a “glitch” or mutation in the mitochondrial DNA, leading to mitochondrial dysfunction.

“Unlike most of our DNA, which we inherit from both parents, mitochondrial DNA is passed down to the child from the mother... The severity varies because of a phenomenon called heteroplasmy, where some mitochondria in a cell might be healthy while others are faulty. The greater the number of non-functioning mitochondria in a person’s tissues, the more severe their symptoms tend to be,” she explained.

When she was told seven years ago that she had MERRF, Ms Chua, now 20, was not “shocked or surprised.”

“My mother has the same symptoms, the same condition, and she had (tempered my expectations). She explained that it runs in the family and it was possible I might have inherited it. It just depends on how severe,” Ms Chua, a student of visual communications at the Nanyang Academy of Fine Arts, told ST.

She added that she had always known of her mother’s condition, “but I never knew its name or the cause”. She had seen her mother dealing with it and had often accompanied her to the doctor at the National Neuroscience Institute (NNI) at Tan Tock Seng Hospital during the school holidays.

Ms Chua was initially upset following her diagnosis, but said she understood that there was nothing she could do but accept it, as it was a hereditary condition.

Like her mother, she developed neurological complications including sudden, brief and involuntary jerking or twitching of muscles and the lack of coordination, both limiting her mobility.

Since 2024, she has come under the care of brain specialist Tan Yee-Leng from NNI, who is, incidentally, her mother’s doctor as well.

“Her seizures were first diagnosed and treated in KKH when she developed myoclonic jerks, which are quick, shock-like muscle movements that occur without warning. These became well-controlled after she was prescribed levetiracetam, an anti-seizure medication. She is also more prone to falls as well as blackouts,” Dr Tan said.

Ms Chua said: “I am cautious about what I do these days because I might trip or jerk and fall, but I am grateful for the days that I am well enough to spend with my friends.”

That same year, Associate Professor Rashida Farhad Vasanwala, a senior consultant from the endocrinology service at KKH, started managing her care as well.

Prof Rashida said that although MERRF syndrome does not directly affect bone health, it impairs muscle function and metabolism, reducing mobility, and leads to secondary bone problems such as osteoporosis, fractures, and skeletal deformities from the lack of use.

Prof Rashida, who has been treating Ms Chua for low bone density, said that while Ms Chua had no symptoms or prior history of bone and back pain, or fractures, her MERRF syndrome was the contributing factor for her low bone density.

“She was advised to optimise her weight and vitamin D levels. Once every six months, we track her weight, compliance with vitamin D intake, and assess symptoms of bone and back pain and her weak and fragile bones,” she said.

Dr Koh said that as the defect behind MERRF syndrome is at the cellular level, “the medical world cannot yet fix the source of the problem”.

“Medical care focuses entirely on managing its symptom to improve the quality of life, and support the body’s energy production for the patient. Specific medications are prescribed to reduce muscle jerks and epilepsy; the patient is put through physical and occupational therapy to maintain muscle strength, flexibility and independence for as long as possible; and given nutritional support to ensure that the diet supports energy needs and avoids metabolic stress,” she said.

Dr Tan said treatment plans for MERRF syndrome patients tend to be individualised, such as symptomatic treatments with the use of anti-seizure medications to address the muscle jerks and seizures.

“Drugs that may worsen (the jerks and seizures) or give rise to mitochondrial toxicity are avoided. Supplements can play a supportive role to enhance mitochondrial function and reduce oxidative stress,” she said.

Prof Rashida added that Ms Chua was initially prescribed vitamin D3 2000 IU, a common daily dietary supplement used to boost healthy vitamin D levels, supporting immune health, strong bones and teeth and muscle function.

This was in view of insufficient levels of vitamin D in Ms Chua’s body.

“After two years of follow-up, her repeated scan that measures bone mineral density showed it had worsened, increasing her risk of fractures from weak bones. She was admitted for her first bisphosphonate infusion in February (2026), to help improve low bone density by slowing down the bone tissue breakdown process, allowing bone formation to catch up and strengthen the bones overall,” Prof Rashida said.

The infusions are given every six months for one to two years until Ms Chua’s bone density improves or normalises.

She said she now takes life “one day at a time”.

“As an art student, while the different layers (of the artwork) dry, I usually take a short tea break as I wait. If I have long painting sessions, I would support my arm on the table for more stability, but sometimes it may not help as my wrist will still jerk. Sometimes when I paint, it will take some trial and error to get it finished,” said Ms Chua.

“I am not exactly sure what the future holds. Yet to me, life is like an empty canvas filled with endless possibilities, and shaped by the choices I make.”

ST Medical Mysteries

KK Women's and Children's Hospital