Meet the 5-year-old boy who has to avoid scary movies and trick or treaters due to a rare brain disease which means he could literally be scared to death. Reed Havlik is one of only 200 people worldwide who have Vanishing White Matter (VWM) disease - a condition that means their bodies nerves deteriorate and disappear.

There is no cure and or treatment available - and it is so unusual because a bump to the head, a fever, and a fright can cause a rapid deterioration, coma or death.

Reed's mom Erika, 33, said this means that the family and his teacher have to be really careful, especially around Halloween. A serious scare from a trick or treater could cause a stress on his brain that speeds up the progression of the disease or put him in a coma.

"We have got to be really careful what we expose him to because he could be frightened to death," Erika Havlik, of Iowa, said. "The stress of it all can speed it [the disease] up. We do celebrate Halloween but only on a really small scale. Reed is going to be Mickey Mouse this year. His school throws a party which everyone dresses up for but everyone there is super helpful."

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"They make sure that the costumes aren't too scary," she said. "They really do understand how serious it is for him."

Vanishing White Matter (VWM) disease is genetic and affects one in every 40 million people.

The body doesn't produce a substance that insulates the nerves in his body, meaning they deteriorate and disappear, and cells in the brain are particularly vulnerable.

Up until the age of 2, Reed was a "happy, healthy little boy" who was full of life and had hit all of the big milestones during childhood. However, after waking from a nap on Nov. 1, 2014, Havlik noticed that Reed was limping and took him to see his doctor.

Medics initially thought that Reed had a small fracture and put his leg in a cast for two weeks. But when the cast was removed, he could barely walk at all.

Over a series of weeks, Reed underwent multiple tests with doctors struggling to find an answer for the tot's troublesome mobility issues. Havlik and husband Jesse, a technology officer, were finally referred to see specialists at the University of Iowa Children's Hospital in February 2015.

Harvik's doctors said the disease will likely kill him in three to seven years.  (SWNS)

It was there that an MRI scan revealed the devastating reality of Reed's rare, terminal illness.

Havlik said she had "never heard" of VWM, but as doctors explained the tragic prognosis of how the disease will eat away at her beloved son's brain she "sat there in shock".

He has now been living with the condition for three years and doctors predict he could tragically die from the disease within three to seven years.

"We have been told that it will eventually kill him", said Havlik, who works in customer service.

VWM eventually leads to organ failure as the white matter in Reed's brain disappears over time.

This means his brain will be unable to communicate with his body and as the disease progresses, he will slowly lose the ability to talk, eat and eventually breathe.

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Reed has already lost the ability to walk and is confined to a wheelchair.

A stress on the brain, like getting frightened, a serious illness or a bump on the head, can cause the disease's progression to speed up. Getting frightened can be so dangerous for Reed that his school has to go to extra measures to make sure the school's mascot - a hawk - if kept well out of his sight.

The youngster is "petrified" of the huge hawk costume, according to his mom.

Speaking of finding out he had the disease, the mom-of-one, added: "It was gut-wrenching. Sickening."

"We had so many hopes and dreams for him but they all vanished in that moment," she said. "It was really hard to take. I almost felt like a zombie. I was just thinking, 'what do we do now?' There's nothing we can do to help him.

The family is concentrating on making memories and taking trips with him before the disease robs him of his ability to see, talk and hear.  (SWNS)

"I still haven't prepared myself for when that day, when he does leave us, comes," she said. "I try not to think about it. I do wonder how I will cope. We will have to redefine who we are and I wonder what life will be like without him. I haven't thought about a funeral. I've struggled to come to terms with it."

Ever since his diagnosis, Reed's desperate parents have "dedicated" each day to giving their son the "best life we possibly can".

"We have been told to try to make the most of our time with Reed. We want to give him the best life we possibly can and enjoy him whilst we can," Hevlik said. "I have good days and I have bad days. I struggle with jealousy a lot. I wish he could play outside and run around like every other 5-year-old."

"We are trying to give him as many opportunities in life and try to soak up every second we have with him," she said. "Our world has been altered completely. It's been life-changing. Everyone has been showering him with as much love as they can to ensure he's as happy as possible."

"It almost feels like we won the unlucky lottery. Just because the odds of Reed having this disease are incredibly slim."

The family has been lucky enough to experience some "special" trips since Reed's diagnosis.

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He has visited Walt Disney World in Florida and will be visiting for a second time at the start of November.

Reed has also been able to enjoy a Make A Wish Foundation experience, handed exclusively to children who are seriously or terminally ill.

But long car journeys can be stressful for Reed meaning the Havliks have to be incredibly selective when choosing to take Reed away on trips.

As the months go by Reed will lose the ability to lose use his hands, to talk, swallow, see, hear and eventually his body will shut down completely.

He is often in pain and is sadly already beginning to struggle to talk and write his own name. Like getting scared, illness can cause Reed's disease to get worse. Any damage to his head can "make the disease worse".

Last year Reed came down with the flu, and once he recovered Havlik said she could notice a "decline" in Reed's condition.

But the Havliks are holding onto hope that one day a treatment, and maybe even a cure could be found in time to save Reed's life.

A global research project is currently underway, but a treatment or cure will come at a cost for the 200 families of VWM sufferers.

Speeding up the progress of finding a cure comes at a cost of approximately $2 million, and it's up to the families themselves to raise the funds to save their children.

For these desperate families, it's a race against time. Reed's family and friends have managed to raise an incredible $150,000 towards funding research.

"Even with a terrible prognosis, there is hope. We will continue to fight for Reed and the research, and try to raise as much as we can," Havlik said. "The research is underway. We can only hope that before it's too late there can be a cure found to slow down the progression of the disease."