BOSTON -- With baseball season in full swing, a local umpire is getting ready to call the last game of his career.

NewsCenter 5's Liz Brunner reported that Walter Bentson won't retire after nine innings this weekend. He plans to umpire 100 straight innings as part of a marathon fundraiser for the neuromuscular disease ALS. What makes his story even more inspiring is that Bentson suffers from an even rarer form the disease.

Bentson is training hard for the last baseball game of a long successful career.

"I'm determined to give it my best shot," Bentson said.

Bentson is an umpire with 3,000 games under his belt. Bentson suffers from PLS -- primary lateral sclerosis -- a very rare form in the same family as ALS.

"In ALS patients, generally, they have a progressive course that is usually fatal. In PLS patients they have a very protracted course that usually is not fatal," Beth Israel Deaconess Medical Center's Dr. Seward Rutkove said.

"My legs, especially, I shake sometimes. Over the last year my speech is slowing down," Bentson said.

It has made calling baseball games increasingly challenging. In a normal summer, Bentson would umpire more than 200 games. Last year, he had to cut back to about half that. But as he prepares to take the field for the last time, Bentson is counting his blessings.

"In many respects, I have been lucky in that so many people who have had ALS, unfortunately, are gone, and my situation with a PLS diagnosis that's been progressing much slower. And I've wanted to do something for many of the victims' kids," Bentson said.

Saturday's matchup, which will last about 30 hours, will be Bentson's way of giving back to the sport that gave him a lifetime of enjoyment. He hopes to raise money and awareness for the illness that has become his toughest opponent.

"This game will make it easier for me to say, 'Alright, after 3,000 games it's a good way to end," Bentson said.

The future is still uncertain for Bentson. Many PLS patients eventually progress to a deadly ALS diagnosis. But for now, Bentson is focused on just getting through 100 innings of baseball and raising $120,000 for ALS and PLS.