Four-year-old Katie Archer is given a birthday party every weekend because her family has a lifetime of birthdays to make up for.

Parents Brett and Lisa are coming to terms with a diagnosis of late infantile Batten disease - an extremely rare degenerative neurological condition which affects only one other child in New Zealand.

The disease will take Katie's sight, her control over her body and mind, and by the age of 10, it will take her life.

"It's destroying to see your beautiful, healthy child deteriorating. We've spent a lot of time crying," Brett said.

His wife added: "As parents you look after your child, give them everything you can and try to set them up for a good life - and we can't do anything to help her."

Finding out what was wrong with Katie was an emotionally-charged process.

She had been having seizures for about a year and was developmentally lagging.

During hospital testing she was checked for pigmentation in her eyes, which can be an indicator of Batten's.

After a sleepless night, the Archers were told her retinas were clear, and felt a huge sense of relief when they thought the worst-case scenario was ruled out.

However, test results from a subsequent spinal tap came back positive for the deadly disease at the end of August.

Lisa said, as horrific as the diagnosis is, at least they are now dealing with a known quantity.

She said they know the path Katie's life will take.

What they don't know is the timeframe.

Four weeks ago she could run, now she is lucky if she can walk without falling over.

She can't communicate and gets frustrated at not being able to do small things like picking up a spoon.

One thing the Archers can do is build memories while they can.

Plenty of family photos are being taken and they try to give Katie as many enjoyable experiences as possible.

Her granddad is giving her lots of tractor rides because it is one of the things she loves, along with the chance to go swimming and visit the zoo.

Katie is much-loved by siblings Caleb and Amy, who understand she is not going to get better.

Caleb was devastated at the news Katie wouldn't be joining him at Bayfield Primary School when she turned five.

The level of care Katie needs is all-consuming, so Lisa has given up her part-time job. Brett, who works from home, has had to give up other commitments like his role on the school's board of trustees.

There are nine health professionals who come into their home on a regular basis including a physiotherapist, speech therapist and occupational therapist.

Through the "living hell" they have endured, the Archers have been floored by some of the kindness they have received.
 
Neighbours who they didn't even know have put themselves on a roster to drop off supplies for them, and a local doctor is calling daily.
 
They are also hugely appreciative of the support of Bayfield Preschool staff who always have their doors open to Katie.

- © Fairfax NZ News