GUILDERLAND — Will Gibney, at 17, has written a book about the dog that changed his life.

“Toshi is my service dog,” says Will in this week’s Enterprise podcast. “He means so much to me because for years he’s been by my side.”

Once Will, at age 12, was matched with Toshi, he began to produce the antibodies he needed to fight infections.

“Toshi has been life-changing for me,” says Will, explaining why he wanted to write the book. He wants other people with disabilities, who may be scared of being ridiculed and judged, to know they can get service dogs to help them.

In the introduction to the book, Will’s mother, child psychologist Laura Assaf, writes, “Will became more independent and mature as he started caring for another being instead of needing everyone else to care for him. The character gifts Will has — his kindness, perseverance, generosity of spirit, and empathy for others — were no longer overshadowed by the incongruent behaviors he demonstrated when his brain was inflamed.”

Will has a condition known as PANS, from which Assaf said one in 200 children may have flare-ups although the syndrome is often misunderstood and misdiagnosed. PANS stands for Pediatric Acute-onset Neuropsychiatric Syndrome.

Will is also immunodeficient, which fewer than 20 percent of children with PANS are, his mother said.

Assaf called it a “double whammy” since her son’s body was unable to produce the antibodies needed to fight infections so he spent lots of time getting infusions to try to build a healthier body. He also underwent seven years of long-term suppression therapy on antibiotics, probiotics, and medications to treat symptoms.

“When there’s inflammation in the body and there’s inflammation in the brain, then we get behaviors” that can often look psychiatric, leading to frequent misdiagnoses of the condition, Assaf said.

When Will’s condition was misdiagnosed by local doctors, his parents pushed to find national experts who understood the condition. Some children with PANS can be treated with a 30-day antibiotic instead of six years on an antidepressant, said Assaf. “It sends them down a very scary and dangerous path,” she said of misdiagnosis.

Will’s book, “My Boy, Will,” captures his five years with Toshi in a narrative written for children illustrated with simple expressive artwork created by Will. The story is told from the dog’s point of view and is at once instructive, entertaining, and poignant.

Will, for example, draws a vacuum cleaner to look like a monster because he imagines that’s how Toshi sees it. Toshi, a Labrador-golden retriever mix, loves to be groomed, so Will draws the brush to look like a shining torch and the dog with a hairstyle that resembles a Tik Tok boy — a swirling pompadour over the forehead.

Will has always liked to draw. “Drawing helps me pay attention …,” he said. “I draw a lot in my free time.”

In addition to Will’s artwork, the text is illuminated with photographs of Will as a boy when he first was paired with Toshi.

The narrative, like the drawings, is simple and direct — often with humor injected.

“When he was not well in fifth grade, Will could not enter his classroom if there were pencils on the floor,” Toshi tells us in the book. “There are always pencils on a classroom floor!”

That page is illustrated with three colorful pencils. The next page is illustrated with the faces of three friends and says, “Since Will is such a cool kid, he had good friends who would run around and clean up the pencils so he would not get stuck in the doorway. But needing friends to do that can make a kid feel sad or weird.”

“Now, looking back, it seems really stupid,” says Will. “But back then I just couldn’t function with my OCD and all these things triggering it.”

Assaf said that the Guilderland schools, and Lynnwood Elementary in particular, where Will was a student, were incredibly understanding and supportive. The school psychologist had Will tell his classmates about his condition.

“So often, with so many of our childhood diagnoses, people don’t want to say it outloud …,” said Assaf, contrasting that to Guilderland’s approach. “He had true peer networking and true social support every step of the way. And that’s why he’s here today, and that’s why he’s going to Siena College.”

Toshi will be going to Siena next year with Will, who thinks he may want to become a lawyer or an author.

“I’m really glad I’ve come this far… and I’m not stopping people from learning,” said Will. “I’m not stopping myself from learning.”

Will’s 15-year-old brother, Dan, has become involved in the Canine Companions program that brought Toshi and Will together. Dan is now raising his third puppy for the program.

He cares for and helps train puppies for the first year-and-a-half of their lives. “We do it so we can change ... the life of someone like my brother or someone who came back from war with PTSD or amputees,” said Dan.

The second dog Dan raised — Dan referred to the dog as a “superstar” — is now in New Hampshire, helping a veteran with post-traumatic stress disorder.

“It’s really sad when you turn them in but you know that you’re doing something amazing just to help one person so much,” said Dan, adding, “But you feel a lot better when you get your new puppy and know that you’re going to help another person after that.”

Dan also said, “I definitely want to keep raising dogs …. It’s going to be weird without Will and Toshi here because she is such a good example for the puppy.”

Will says he knows that Toshi will not always be by his side, and has decided not to get another service dog after him. “I wouldn’t feel right taking another one, since I don’t need one, especially when other people do need one,” he said.

He wrote “My Boy, Will” for children, Will said, and he hopes it will increase understanding of PANS. He also hopes the book will encourage people with disabilities and support Canine Companions.

Will thinks if psychiatrists and doctors read his book, they would get a better understanding of what it’s like to have PANS.

The Gibney boys gave thoughtful answers when asked what they have learned from their dogs.

Will said he had learned to control his impulses and learned “a lot more responsibility.” “You have to be vigilant,” he said of caring for a dog.

Dan said he had learned patience, explaining that puppies don’t understand commands right away.

“One more thing ...,” concluded Will of what he has learned, “It’s OK to fail because you can always try again.”

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William J. Gibney will be selling and signing his book, “My Boy, Will,” at Colonie Center, outside the entrance to Macy’s, on Sunday, Dec. 12, from noon to 2 p.m. The book-signing will double as a seventh birthday party for his dog, Toshi. All of the proceeds from sale of the book are being donated to Canine Companions, which provides service dogs free of charge.