Trisomy 9 Mosaic: Four sufferers of incredibly rare genetic condition call NZ home

Four Kiwi children with an extremely rare genetic condition have met up for a special celebration in Auckland.

They're hoping to shed new light on the little known chromosome disorder which affects just 170 children worldwide.

Nate Ryan-Chang has an extremely rare syndrome called Trisomy 9 Mosaic - T9M. On Sunday he beat the odds and celebrated his fourth birthday.

"To reach four, you go, well that's pretty good," says mum Jen Ryan.

"So it's onwards and upwards really and we take and celebrate every moment that we have with our boy."

T9M is a one in 100 million genetic condition, but the extraordinary thing is, Nate is one of four in New Zealand.

Tegan, Amira and Lily-Grace all have the same rare condition.

"To have four and literally one year apart between each of them is amazing," says Ms Ryan.

Trisomy 21 is Down's Syndrome. Trisomy 9 is much more rare - it means they were each born with an extra chromosome 9, three instead of two, which causes a variety of developmental problems.

"We don't know if they'll ever see, hear, eat, walk, talk, or any of those things," says Amanda Davies, mum of two-year-old Lily Grace.

There are the disabilities you can see and the ones you can't, and it takes a lot of work.

"Therapies daily, speech, physio, OT [occupational therapy] and other speciality special needs therapies, like music therapy," says Ms Davies.

And the costs add up.

"For example many T9Ms don't produce enough melatonin to sleep, but it is not funded in New Zealand and a bottle of the liquid will costs around $100," Ms Davies says.

"Music therapy is amazing for Lily, learning confidence and communication and language but it has a minimum donation of $115.00 per half hour.

"Our hospital system does the very best they can but most Trisomy parents I know end up paying for speech therapy at a cost of around $150 an hour."

Then there's the ongoing medical problems that arise - they have weakened immune systems and often end up in hospital.

But these dedicated parents are determined to make a better prognosis.

"Now when you Google, Trisomy 9 Mosaic, up pops these kids that are smiling," says Ms Davies.

"They do have disabilities and they do need extra help, but they are thriving."

The group wants to raise awareness so they can get better support here and continue to help others around the world.