CLEVELAND -- Former Cleveland Browns general manager Dwight Clark has been diagnosed with Amyotrophic lateral sclerosis, better known as ALS or Lou Gehrig’s disease.

Clark made the announcement on Twitter late Sunday night.

A two-time Super Bowl champion with the San Francisco 49ers, Clark played nine seasons in the National Football League. Over 134 regular-season games, Clark caught 506 passes for 6,750 yards and 48 touchdowns. He averaged 13.3 yards per catch and 50.4 yards per game.

Additionally, Clark caught 48 passes for 726 yards and three touchdowns in nine career playoff games, none bigger than an outstretched reception in the back of the end zone on a pass from Hall of Fame quarterback Joe Montana to seal a victory over the Dallas Cowboys in the 1982 NFC Championship Game.

Clark’s NFC Championship-clinching reception has been referred to as “The Catch,” and remains one of the most recognized plays in NFL history.

Following his playing career, Clark transitioned into the front office, serving as the general manager for the Browns from 1998 to 2002.

“I’ve been asked if playing football caused this,” Clark said in a statement confirming the news. “I don’t know for sure, but I certainly suspect it did. And I encourage the NFLPA and the NFL to continue working together in their efforts to make the game of football safer, especially as it relates to head trauma.

“What I do know is I have a huge battle in front of me and I’m grateful for the strength and unconditional love from my wife. Kelly. She has been my rock. She keeps thinking positive and convinces me each day that we can beat this, as does my daughter, Casey, and my son, Mac. My brother, Jeff, his wife, Debra and their family also have been unwavering with their love and support.”

Discovered in 1869 by French neurologist Jean-Martin Charcot, ALS is a degenerative disease that impairs nerves in the brain and spinal cord. Those suffering from the disease eventually lose all motor functions and the ability to speak.

Eventually, the degeneration of neurons becomes fatal.

Despite the diagnosis, Clark vows to fight with the strength that he has left to find a cure for ALS.

“While I’m still trying to wrap my head around the challenge I will face with this disease over the coming years, the only thing I know is that I’m going to fight like hell and live every day to the fullest,” Clark said.

“I’m not having a press conference or doing any interviews. That time will come. Right now, I’ve got work to do. I’ve got to devote all my energy preparing for this battle, and I would hope you can respect my family’s privacy as I begin this challenge. My ultimate hope is that eventually, I can assist in finding a cure for ALS, which disrupts the lives of so many and their loved ones.”