From the day she was born, Sarah Morrell has exceeded people's expectations. The spirited 16-year-old has Morquio IV – a degenerative condition so rare it affects only one in a million.

It severely limits her growth, but Sarah refuses to let it define her. At just one metre tall, wheelchair bound and having undergone two spinal surgeries to fuse her head to her spine, Sarah has had to overcome more obstacles than most. Yet the Wanganui High School student embraces her differences and, with a passion for travel, dreams of one day helping other disabled people see the world.

'People think that if you're disabled you can't travel,' says the vivacious teen, who has already visited Australia, America and Samoa. 'It's possible, though, so when I grow up I want to become a travel agent to help others go to amazing places.'

Sarah's ambition was ignited in 2009 when she began taking annual trips to San Francisco to take part in Morquio IV research. 'The best part is meeting people with the same condition as me,' Sarah says. 'It's nice to know I'm not the only one like this.'

Sarah's positive outlook has been ingrained in her from the moment her parents, Lynda and Ben, were told of their daughter's diagnosis, when she was 18 months old. 'We focus on what we've got. Not what we haven't got,' Lynda says.

'People often have to redefine what they think a wheelchair person can do when they meet Sarah.' Already parents to a son, Timothy, now 19, the couple were thrilled to be adding a little girl to their family.

After a normal pregnancy and delivery, Sarah's diagnosis was an unexpected blow. A Plunket nurse noticed a curvature in Sarah's spine and, after months of testing, she was diagnosed with Morquio IV.

Sarah is missing an enzyme in her body which causes toxins to build up in her joints, curbing her bone development. The condition is so rare that Lynda, a registered nurse, had never heard of it.

'It was such a shock and difficult to get my head around,' Lynda says. 'I looked at my baby and wanted the best for her in life. We just try to make things as good as they can be.'

Lynda and Ben, both 52, decided to delay medication and surgery until Sarah was five. 'We didn't want to traumatise her or make her miserable,' Lynda explains. 'But it was hard for us knowing that, one day, major surgery lay ahead.'

By the age of five, when most children are starting school, Sarah was preparing to have a life-changing operation to fuse her head to her spine. With her spine too weak to hold her head securely, simply falling over could leave her paralysed.

The family met with Haemish Crawford, Starship's paediatric orthopaedic spinal surgeon. He performed the operation in a way that prevented Sarah from having to wear a heavy halo device bolted into her head.

It was the first procedure of its kind to be done on someone so young in New Zealand. Following surgery, Sarah started using a walker, but over the next few years her condition worsened and she underwent several operations.

'Surgery is challenging,' Sarah says. 'It can be difficult getting back to my normal routine because it takes a while to recover.'

In her final year of primary school, Sarah was struggling to walk and was faced with being confined to a wheelchair. 'In her school production The Rocky Horror Show, Sarah was determined to walk on stage one last time,' Lynda says.

'Although she could barely put one foot in front of the other, she came out on her walker. Everyone clapped. I have never been more proud.' And, since then, Sarah's tenacity has only grown stronger.

'It's been tough here and there, but I just get on with life and do what I want,' Sarah says. 'There is no point in complaining because it is what it is. I love life and hate the words can't and no.'