ALLENTOWN, Pa. >> Former NFL player and general manager Matt Millen says he is being treated for a rare disease that has robbed his heart of most of its normal function.

The 60-year-old Millen told the Morning Call in Allentown, Pennsylvania that he has been diagnosed with amyloidosis, a life-threatening illness that may force him to seek a heart transplant. Millen said he has been receiving chemotherapy once a week to treat the condition that left his heart functioning at just 30 percent.

Millen played 12 seasons as a linebacker in the NFL for the Raiders, 49ers and Redskins — and won four Super Bowl rings.

He later served as Detroit’s general manager and has also spent three decades as a broadcaster. Millen told the Morning Call he plans to return to the booth in the fall.

Millen’s heart issues began in 2011, when he first felt chest pain while exercising. Heart tests, including a cardiac catheterization, showed nothing wrong.

Amyloidosis often goes undiagnosed because its symptoms mimic those of more common diseases. But Millen’s symptoms grew worse over time, and he visited doctors for six years before finally getting diagnosed with the rare disease last July.

“I know what you have,” Millen recalled the doctor telling him, “and you’re not going to like it.”

Millen’s case reached the point where he was risking the kind of heart failure that would eventually require a transplant. Millen spent the week before the Super Bowl undergoing tests at the Mayo Clinic in Minnesota.

“When a bump comes up in the road, you deal with it,” Millen said. “It’s ridiculous to feel sorry for yourself. I’m thankful for what I have, and I’ll take what I get.”