Ten-year-old Boon Kye Feng prances around the living room in furry purple pants that match the lion's head he is wearing.

He lifts the head and moves it from side to side to a beat only he can hear.

Even when the little lion gets thirsty, he drinks water through the opening in the head.

Seeing him at play, it may be difficult for strangers to tell that he has spent almost half his life battling leukaemia.

His family fought it along with him, gifting two transplants - cord blood from his baby sister and stem cells from his mother - to keep him alive.

MIRACLE BOY

I believe Kye Feng is a 'miracle'. We have all learnt a lot from him, not only in the science of managing the disease and the doctor-patient relationship, but also in his love of life, and his fearlessness and resilience, despite the years of pain and suffering.

ASSOCIATE PROFESSOR TAN POH LIN, from the paediatric haematology- oncology division of NUH.

Despite the intensive treatment, his parents said he had remained positive and playful.

It had started in late 2011 when Kye Feng developed spots and bruises which his parents thought were sandfly bites.

When the spots appeared a second time, his mother, Mrs Celine Boon, decided to take him for a check-up.

Doctors found that his white blood cell count was very high and told the family he could have leukaemia (cancer of the blood).

It was diagnosed as juvenile myelomonocytic leukaemia (JMML), a rare form of the disease.

But Mrs Boon, 38, was not too surprised.

This was because Kye Feng and his twin brother, Kye Teck, had previously developed juvenile xanthogranuloma (JXG), a skin disorder that is usually benign and self-limiting.

They also have an older sister, now 16, who was unaffected.

While reading up on JXG earlier, Mrs Boon had come across a potential link to JMML.

She said: "Still, I had never expected that it would happen to my son. I was quite alarmed."

JMML is so rare that blood samples had to be sent to Germany to confirm the diagnosis.

Kye Feng began chemotherapy at KK Women's and Children's Hospital (KKH) in 2012 to control the condition while waiting for a bone marrow transplant.

Although KKH doctors had not seen a JMML case in about 10 years, they did the transplant as there were few other options.

His father, Mr Roy Boon, 46, said: "It was all trial and error. There's no exact treatment for JMML."

Mrs Boon was then pregnant with their fourth child and doctors said the baby girl's cord blood could be used for the transplant as there is a 25 per cent chance of a match between siblings.

Juvenile myelomonocytic leukaemia (JMML) is a very rare form of childhood leukaemia. The hallmark symptom of the disease is the increased number of white blood cells known as monocytes.

Normal monocytes protect the body from infections, but those in patients with this leukaemia are cancerous and reproduce uncontrollably. The monocytes may then infiltrate organs such as the liver, spleen, lungs, lymph nodes and even skin.

In Western countries, one in a million children are afflicted with the disease each year. Based on Singapore population statistics last year, there is an average of one case every three years.

For the majority of JMML patients, a haematopoietic - or blood forming - stem cell transplant (HSCT) is the only curative option.

Stem cells are cells that have the potential for self-renewal and differentiation. They can develop into different forms, including white blood cells, red blood cells and platelets. Such a transplant can help patients develop new and healthy blood cells.

Stem cells can be found in the bone marrow, blood, fat tissue and placenta. They are abundant in the bone marrow but, even so, make up only 1 per cent of all cells there.

They can be "harvested" directly from the bone marrow or from the blood, whether they are from an adult volunteer or from umbilical cord blood.

The bone marrow must be stimulated to coax or force the stem cells into the peripheral blood system, but techniques are well-tested and safe.

After undergoing HSCT, 50 per cent of the patients will go on to become long-term survivors.

Abigail Ng

Source: Associate Professor Tan Poh Lin, senior consultant at the division of paediatric haematology-oncology, National University Hospital.

Thankfully, it was a full match for Kye Feng, who had the transplant and recovered well.

He looked forward to starting Primary 1 with his brother.

But before the March holidays of his first year in school, doctors noticed that the percentage of donor cells in him was beginning to fall, signalling that there could be a problem.

When it became clear that the cancer had returned, Mrs Boon said she broke down and cried.

"I was shocked. There weren't any physical symptoms. Why did it happen so quickly? It wasn't even one year after the transplant and things had looked so promising," she said.

A SECOND CHANCE

The family sought a second opinion from the National University Hospital (NUH) and entered into the care of Associate Professor Tan Poh Lin from the paediatric haematology-oncology division.

While doctors from both hospitals suggested a second transplant for Kye Feng, there was more bad news.

His illness was mutating into mixed-phenotype acute leukaemia, a combination of two forms of cancer.

He also faced a life-threatening infection that caused high fever and bloating.

Besides beginning palliative care to improve his quality of life, the family continued to push for treatment, including natural killer-cell therapy and the removal of Kye Feng's enlarged spleen in a complicated seven-hour operation.

Even though the test results showed that leukaemic cells remained in his bone marrow, Kye Feng had a second transplant in September 2015, this time using stem cells from his mother.

Doctors usually recommend transplants only when patients register no leukaemic cells.

Mrs Boon said: "If he didn't have the transplant, he would have only six months more. With the transplant, he would at least have a chance of recovery.

"He was fighting hard. If I didn't give him the chance, I would never know if he could have survived."

Kye Feng responded well to his mother's stem cells.

Dr Tan said: "I believe Kye Feng is a 'miracle'. We have all learnt a lot from him, not only in the science of managing the disease and the doctor-patient relationship, but also in his love of life, and his fearlessness and resilience, despite the years of pain and suffering."

The crucial three months after the transplant passed by without issue, but the boy developed a graft versus host disease (GVHD) one year later.

Still, his parents were relieved that it was not a second relapse.

He was put on medication for GVHD and will recover completely.

In the meantime, the family is treasuring the time they can spend together.

Mrs Boon said: "We will relax and go with the flow, as long as Kye Feng is happy."

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Lion-hearted fighter beats the odds - The Straits Times

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