PROVO — Six-year-old Brigham Reneer is very much like the Tarzan character he idolizes.

He's tough, brave and he lives in a place fraught with peril — except Brigham Reneer's jungle is a maze of medical tests and painful procedures.

His friends are the make-believe wild animals hidden in the foliage. And his foes are leukemia and a rare disease that will kill him in a few years.

The strong little boy, wearing the leopard-skin robe, has Hunter syndrome, a severe form of a mucopolysaccharide disorder.

That means he's missing the enzyme that usually provides for the regeneration of connective tissues. Instead of regenerating, the mucopolysaccharides in his body remain stored in his cells, forcing his limbs to stiffen, facial features to broaden, brain to lose function and, eventually, his heart valves to shut.

Reneer was diagnosed with the disorder at 3 years old after his parents, Randall and Julie Reneer, took him to Primary Children's Medical Center to talk to doctors about his leukemia.

"He really got a double whammy," said his mother, Julie Reneer. "The doctors say they see children with leukemia and children with (the disorder) but never both."

Hunter syndrome is genetic and specific to males, but Brigham's little sister, Emily, could be a carrier of the MPS.

"It is genetic, and it's awful," said Julie Reneer. "The storage takes over. His whole life is pain. He has spinal taps without general anesthesia because of the leukemia, and although the leukemia is under control, the MPS is out of control."

Because Brigham Reneer's disorder is incurable, the family chose to take him off chemotherapy for the cancer after two years. Usually, the therapy goes for three years.

"He's doing really well, and we can't see making him suffer any more than he has to," Julie Reneer said. "Our goal with Brigham is to just give him the best quality of life while we have him."

Brigham, a strong and busy boy, easily climbs the steps to his new boat treehouse in the family's shady back yard and relishes the fast trips across the lawn in the zip line swing.

"This is great therapy for him, going up and down, besides just being so much fun," said Julie Reneer. "The more he moves, the more active he is, the better."

He's playing on "Brigham's Tarzan Treehouse," which is designed to look like the shipwrecked boat in which Tarzan lived. It was paid for by Utah's Make-A-Wish Foundation.

Students at Brigham Young University hauled in boulders for a terrace, and neighborhood families dug holes for seesaw toys. Others donated landscaping materials, trimmed trees and added the swing and a slippery slide.

There is a covered sandbox and carved stone animals — an alligator, elephant, orangutan and gorilla — in the yard.

Brigham Reneer spends a lot of time in the treehouse, sharing the fun with his sister who plays Jane to his Tarzan.

"It's become his sanctuary," said Julie Reneer. "He loves it. It's his 6 1/2 birthday gift. We double up because he won't have that many birthdays."

Brigham Reneer recently underwent carpal tunnel surgery on his wrists to relieve pressure on his hands. He's starting to speak thickly.

"He loves to sing, to laugh, to play. He loves life," said his mother. "But it's happening. His joints are stiffening. His features are coarsening."

In Brigham's lifetime, the Reneers don't expect a cure for MPS to be discovered — but that doesn't mean they aren't hoping for more miracles.

"We have incredible faith, and we still believe in miracles, although we're very much at peace with this," Julie Reneer said. "Miracles come in lots of ways. This is a miracle," she said, waving at the treehouse. "He's a miracle, how strong he is, how happy he is."