An East Tennessee woman is defying doctors' expectations and returning to work, driven by her passion for the job and helping others.

Tiffany Russell is an E-911 call processor with the Knox County emergency communication district.

She collapsed on the job in January with a then-unknown medical problem, and doctors told her she would probably never walk again.

Through physical therapy, this 23-year-old got back on her feet and returned to work in late March.

Then, in June, she collapsed on the job again.

However, she was determined to come back to work, and on Monday, that's just what she did.

A person has to be at least 19 years old to work as a call processor at Knox County's emergency communications call center.

Russell started 5 days after her 19th birthday, in May of 2012.

"I love helping people and I've always wanted to work in law enforcement," she told WBIR 10News Monday.

Doctors diagnosed her with three serious and incurable conditions after she collapsed at work twice this year: autonomic dysfunction, Addison's disease and the vascular type Ehlers-Danlos syndrome.

She returned to work Monday wearing a hygienic mask because of a compromised immune system.

"I've gotten used to it. I've been wearing it now for probably for three weeks," Russell said. "I have no immunity. I got a common cold and it sent me to the ICU for a week."

Alan Bull is interim director of the Knox County emergency communication district.

He said Russell "loves people, loves what she does."

He called her return to work miraculous.

"You know, throughout the whole thing, she never lost faith," Bull said.

"Everybody is meant to walk a certain path in life, and everybody has a purpose in life," Russell said, "so I'm just going to walk my path and purpose that God has put me on."

During her many hospital stays, Russell spoke regularly with her colleagues, whom she calls her family.

"We stayed in touch and made sure that she knew we were looking forward to her coming back as much as she was looking forward to being back," colleague Josh Biggs said.

Co-workers pulled together to help support Russell, in friendship and with finances.

"People donated annual leave and sick leave to her. They took up collections. We made sure her insurance was paid," Bull said, adding the team even held a blood drive in her name.

"I'm very thankful for them," Russell said. "I could never thank them enough for all that they've done for me and supported me along the way. I couldn't have made it without them."

In this emergency call center, the smiling eyes above Russell's sterile mask communicate the thanks and appreciation that words alone cannot.

Russell, who lives in Campbell County, has a 2-hour round-trip commute each day, saying she likes working in a bigger city. Her aunt works at the Anderson County E-911 call center.

Russell is also a full-time nurse practitioner student at South College, taking online classes. Before her hospitalization, she had a 4.0 GPA and managed to maintain a 3.38 GPA through all of her procedures.

Now she's taking it easy, easing back into the job with shorter shifts.