​SINGAPORE – Siblings Eugene and Angie Lim, who are in their 20s, inherited an incurable disease from their mother.

At least three generations of their family have been affected by the genetic condition neurofibromatosis (NF), which causes multiple tumours to form on nerve tissue. While many sufferers have mild symptoms, there is a small risk of some tumours becoming cancerous.

Eugene, 26, and Angie, 25, have a genetic disorder called neurofibromatosis type 1 (NF1). It is characterised by brown patches on the skin known as "cafe au lait" spots – which means "coffee with milk" in French – as well as tumours called neurofibromas, which appear as rubbery lumps on or under the skin, which may be itchy or painful.

An affected parent has a 50 per cent chance of passing the disease to his or her children, although some sufferers do not have a family history of it. There is no cure, and treatment involves monitoring and treating problems should they occur.

NF1 is more common than other forms of the condition, neurofibromatosis type 2 (NF2) and schwannomatosis.

Skin symptoms are much less common in NF2, where most sufferers develop benign nerve tumours in the ears, which can result in hearing loss or tinnitus. In NF2, tumours can also develop in the brain or along the spine. In schwannomatosis, a key symptom is debilitating pain caused by tumours growing and pressing on nerves and tissue.

In Eugene and Angie's recollection, the genetic condition stretches back to their maternal grandmother, who passed it on to her two children – their late mother and their uncle.

The siblings' mum, from whom they inherited the gene mutation, died at age 47 in 2016 from a malignant peripheral nerve sheath tumour, a rare cancer commonly associated with NF1. Their grandmother died in her 70s a few months earlier that same year, though they do not know what kind of cancer she had.

Although neurofibromatosis runs in their maternal lineage, they say members of their conservative, traditionally Chinese household never discussed their genetic burden.

Before Eugene, who works part-time at a student care centre, and Angie, an assistant engineer in the waste-water treatment sector, were diagnosed with NF1 in primary school, the family spoke of it only as a "skin disease" that had been handed down the generations. The siblings' father, 64, is a retired kitchen assistant.

Talking to The Straits Times in connection with Neurofibromatosis Awareness Month – which is observed in various countries, including Singapore – in May, the siblings say it is important to speak up about having the condition. For decades, the topic was shrouded in silence in their extended family.

Eugene says: "Many medical matters are taboo to talk about among friends and family. But I would advise that people with NF speak about their condition when others ask them, as not a lot of people know what NF is."

When Angie was in Primary 1, officials performing routine health checks for her cohort found brown spots all over her body.

She was not concerned. "I told them these are just birthmarks. That's what my mum told me."

Her brother, who was in the same school but in Primary 2 at the time, had fallen under the radar a year earlier, but their mother told the doctor they consulted that Eugene had similar symptoms. The children, then aged seven and eight, were diagnosed with NF1.

Most of the spots on their skin are covered by clothing, although some are visible on their face, neck and arms. Their neurofibromas, often manifesting as pea-sized tumours, are under their skin.

It was only after the children were diagnosed that their mother and grandmother learnt the name of the condition they all had, say the siblings. The women did not receive treatment for NF1, even though their tumours caused them discomfort.

Angie recalls hearing her mother praying that her children would not get the disease she had, even though Angie has had cafe au lait spots ever since she can remember.

Angie says: "I think she knew we had it even before our check-up. We felt there was no need to talk about it. We didn't pry, out of respect for my mum. It was normal for our family."

Eugene adds: "My mum didn't want to talk about it. I think she did not want to scare us. She could have been scared as well."

Dr Chiang Jianbang, a medical oncology consultant at National Cancer Centre Singapore (NCCS), says that while NF1 is usually picked up in children and adolescents on account of their spots, diagnosis can be challenging, especially if the individual presents with mild symptoms.

He says: "The severity of symptoms associated with NF1 can range from extremely mild to severe, and vary within individuals of the same family. Some patients may have only small, isolated skin patches and lumps, while other patients may have multiple lesions over their body.

"These lesions have the potential to become cancerous and patients need frequent follow-up visits at the clinic. Generally, the sooner someone is under the care of a doctor trained in managing NF1, the better the outcome."

Cancers can develop in 8 to 13 per cent of patients with NF1, he adds.

Ms Manasadevi Karthikeyan, genetic counsellor at the cancer genetics service at NCCS, says: "NF1, the most prevalent type of NF, occurs in approximately one in 2,500 individuals globally. There has been an increase in NF1 patients at NCCS due to the set-up of a dedicated clinic to manage adult patients with NF1."

The cancer genetics service now manages over 40 families with NF1, she adds.

Within their family, Eugene and Angie have found that the visibility of a disease can make a big difference in how society treats them.

The pair faced bullying and rejection in primary and secondary school on account of a few spots on their faces and arms. But they think their mother and grandmother – whose NF1 symptoms were far more evident, including lumps and patches that spanned their faces and bodies – had it worse.

Angie says: "We had some teasing in school, but it was not to the same extent. That's why it was hard to relate to my mum and grandmother's experiences. When we went out, people would always stare at them."

Even though their own physical symptoms were mostly covered up, "it was enough for kids to see that you're different", says Eugene.

The siblings were called "alien" and "ugly", and their schoolmates spread lies that their disease was contagious. They got through years of bullying through the support of friends in church.

The siblings, who are both single, stress that they harbour no resentment towards their mother, whom they were close to and remember as a joyful person who taught them her hobbies of knitting and arts and crafts.

They still have trepidation about the future, however.

Eugene says: "One of my fears is that the tumours may become cancerous, which was what happened to my mum."

He adds: "If I wanted to have children, would my children have the same symptoms, or more severe ones?" He is still mulling over whether to become a parent. Angie has similar concerns.

Their bond has been strengthened through being "caregivers" for each other, as both have undergone surgery to remove tumours over the years, says Angie.

She adds: "After my surgery in secondary school, we started to talk more about our condition and would inform each other if we felt any discomfort, found new lumps or discovered that some lumps had grown bigger.

"Family support is important. Having a brother who has the same condition made me feel less alone."

Angie says: "It is important to have open conversations and support. After I learnt that my condition was NF – and not a skin condition, as my mum and grandmother assumed – I joined NCCS support groups and NF groups on Facebook. I wanted to get information from people who have been though similar experiences.

"From their sharing, I was heartened to know that I, too, can live a normal life and pursue my dreams, such as graduating from university, joining the workforce and developing my expertise in civil engineering."

National Cancer Centre Singapore and KK Women's and Children's Hospital are organising a talk, Living With NF, on May 18 at National Gallery Singapore. It will be followed by a Shine A Light On NF Walk around the Central Business District (register at bit.ly/nf24registration). Shine A Light On NF is a global movement that promotes NF awareness by lighting up buildings, bridges and monuments in blue and green. In Singapore, landmarks like the Singapore Flyer, Gardens by the Bay and the Merlion will be lit up at night on varied dates from May 13 to 19.