Neighborhood holds Halloween party in May for boy with rare condition

"We are trying to make as memories as we possibly can," mom Jen Sarkar said.

— -- A California boy received an early birthday present on Sunday, when his neighborhood celebrated his favorite fall holiday five months early.

Carter Sarkar suffers from Sanfilippo syndrome, a rare metabolism disorder in which the body cannot break down sugar molecules. There is no cure, and Carter’s life expectancy is mid-to-late teenage years.

On Sunday, Carter’s family, friends and community trick-or-treated in May for his Halloween-themed party, just days before his fifth birthday.

"With where is he right now, he's still speaking and walking ... we are trying to make as many memories as we possibly can," mom Jen Sarkar of Castaic, California, told ABC News. "We are just humbled for the outpouring of love and support everyone has shown Carter and our family."

Carter was diagnosed with Sanfilippo syndrome on May 11, 2016. Carter is expected to lose his speech, ability to walk and may develop seizures, in addition to other side effects.

"It is caused by an enzyme deficiency where the children don't have enough of an enzyme to break down normal byproducts of the cell metabolism," said Cara O'Neill, pediatrician and the scientific director at Cure Sanfilippo Foundation. "It builds up and causes damages to the cells, but particularly brain cells."

O'Neill, a resident of Columbia, South Carolina, has a daughter Eliza, 7, who also has Sanfilippo syndrome. O'Neill told ABC News that she has met Carter and the Sarkar family.

"He's an absolutely adorable, vibrant little boy," she added. "His parents are fighting very hard to find a path that works for him that doesn't involve suffering and that's what all of us are trying to do as we work toward funding research and advocating."

At this time, O'Neill said there is no cure or treatment for the condition. There are some clinical trials, but because Carter has a secondary condition (pancreatitis), it excludes him from participation in those trials.

Before symptoms begin to surface, Carter's mom and loved ones decided to give him a birthday he'll never forget.

The entire block participated in trick-or-treating and dress-up for the makeshift Halloween. Carter went as Darth Vader of "Star Wars."

"There is a reason why his birthday dream came true and we couldn't have done it without [the community]," Sarkar said.

Sara Mallon, the Sarkars' next-door neighbor, said she and her four children participated in Carter's Halloween birthday party.

"I thought it was a fun way to spread awareness of Carter," Mallon told ABC News. "We've known their family since before Carter was diagnosed. We love Carter and it just has been so neat to see how they've embraced this challenge. Whether there's a cure for their son or not ... they're ambassadors for Sanfilippo syndrome."