Ethan Rosenberg, 2, is one out of a dozen or so people in the world with the diagnosis of Spastic Paraplegia, a rare brain disorder that causes microcephaly, weakness of the leg muscles and developmental issues.

But his parents didn't find out until Dec. 23, 2016, more than two and a half years after Ethan was born.

Ethan's parents began to notice something was wrong when the toddler failed his two and four-month-old milestones.

At first, Matthew and Suchan Rosenberg were not concerned.

"We just thought some kids are delayed and not everybody follows the same timeline so we thought at that point we were just getting some extra help for him," Suchan Rosenberg said.

But that soon changed after an MRI showed damage to Ethan's brain. The toddler was also not developing well. His head was small and he was eventually diagnosed with autism.

Currently, Ethan is in weekly occupational, speech and behavioral therapy sessions. He started occupational therapy at five-months-old.

"When he first started, he couldn't pick up the shoe, he couldn't follow the direction to put it in the box. It was kind of we hold his hand and put it in and now he's doing it really great," said Noelle Alexander.

Alexander is one of Ethan's therapists at First Leap, a pediatric therapy facility in North Austin.

As Ethan continued therapy, Suchan buried herself in research and found the Discover Program at Columbia University in New York City. It offers high-quality medical care for patients with undiagnosed conditions.

That's where they met prominent geneticist, Dr. Wendy Chung.

A whole exome sequencing was done on Ethan; it's a test that gets information from his genes.

And on Dec. 23, Dr. Chung told the Rosenbergs that Ethan had a gene that caused a neurological disorder called Spastic Paraplegia.

"It's very rare... Of the ones that we actually know of - so they know their diagnosis - we know they're out there, there can't be more than about a dozen or so," said Dr. Chung.

The Rosenbergs weren't prepared.

"It was just another punch in the gut. I feel with Ethan, he's made incremental progress but not enough to blow your mind. And so with the Autism diagnosis, the seizures, with the spells and then this," said Matthew Rosenberg.

Because the testing for Ethan's gene, SPG47, just started, doctors believe there are thousands of families affected and don't know it yet.

The Rosenbergs want to raise awareness about SPG47 and want other families with undiagnosed children to get genetic testing.

The Rosenbergs are glad they finally have answers to why Ethan could end up in a wheelchair.

But no one knows for certain since Spastic Paraplegia was only discovered within the past five years.

That's why the Rosenbergs also said it is important to raise money for research because it's the only way to find more information and eventually a cure.