By Gary Haber

There’s a saying that goes, “If you’ve met one person with autism, you’ve met one person with autism.”

That’s because the condition is so individual for each person on the autism spectrum.

In his new book, “Mariel: An Autistic Woman’s Inspiring Journey,” Holtsville author Mike Costanza tells of his experience in raising a child with special needs and how his daughter’s autism diagnosis hasn’t kept her from pursuing her passion for singing.

While she was nonverbal at age 5, Mariel Costanza, now 39, has twice performed “The Star-Spangled Banner” before Mets games at Citi Field, opened for a Lynyrd Skynyrd tribute band at Smith Point Park and sang at area music venues including 89 North in Patchogue.

A professional singer, she’s performed both as a soloist and as part of a rock band called Rock Paper Scissors.

Mike Costanza said he wanted to share Mariel’s story “to inspire not just parents of autistic children, but any parent who wants their children to reach their highest potential.”

Writing the book took about three years, said Mike, a real estate broker. He called the experience “cathartic.”

Things haven’t always been easy since Mariel’s autism diagnosis when she was about 2 and 1/2. A low point came in 2011 when Mike’s wife and Mariel’s mother died suddenly, leaving father and daughter to wonder about the future.

“Who’s going to take care of me?” Mike remembers Mariel asking.

Mike, now a single father to an adult with autism, had the same question.

It’s a question an increasing number of parents ask as the number of people diagnosed with autism grows. Currently, about 1 in 36 children and 1 in 45 adults are on the autism spectrum, according to the Centers for Disease Control.

Costanza said he’s gotten good reactions from people who’ve read the book since it was published on Sept. 1.

“It’s just really heartening to see people take inspiration from the book,” he said.

“Mariel: An Autistic Woman’s Inspiring Journey” is available on Amazon and at www.marielbook.com. A portion of the proceeds from the book will be donated to Autism Speaks, Costanza said.