Sometimes the disease is caused by smoking, but in Smith's case, there was no known cause, making it the idiopathic.
"In some cases it may respond to immune-suppressive therapy, but transplant is the only option especially for patients like Mr. Smith," she said.
As Doug's disease worsened, doctors told him to think about a lung transplant. His breathing was so bad he could barely leave the house.
Budev put him on the transplant list June 18 and because of the severity of his condition he was in the top 10 percent, and the call came three days later.
For 41 of the 46 days in the hospital, Smith had a tracheostomy or ventilator to help him breathe. Even after he was released from the hospital, the couple had to live in a nearby hotel to make sure his condition was stable.
Today, three months post surgery, Susan Smith is back at work at Home Depot and Doug Smith is hoping to return to work.
Despite being on multiple medications, he said he "feels great. ... I still feel weak in my legs, but I am going to rehab three days a week. I am very hopeful."
The couple wanted to share their story to raise awareness about pulmonary fibrosis and to encourage others to become organ donors. Susan Smith said her son had been an organ donor before he was murdered at 18, but because of the crime investigation and autopsy, his organs were never used.
"I never knew how important it was until I had a co-worker with a pancreas donated because he was going to die," she said. "It's about saving lives and we need to get the word out."
Susan Smith admits it's been a "long road" to recovery, but she praises the staff at the Cleveland Clinic.
"It's amazing, the way they took care of us -- even me," she said. She stayed by her husband's side throughout the medical ordeal. "They don't just take care of the patient, but the person who is with them. They were always looking out for me, too."
The couple is busy planning a benefit event to help pay for medical bills and said they have received generous support from family and friends.
"I am so grateful," she said. "I thank God for his second chance, and we are looking forward to a good future."
She remembers the hard days before they were married when her husband's health was on the decline.
"He made funny remarks that I don't know what I got myself into," she said. "But everything happened the way it was meant to be. I am supposed to be where I am."