"There can be a whole spectrum as to how this can first present," said Dr. Carol Langford, a staff physician in rheumatic and immunologic disease at the Cleveland Clinic.
She explained that some people may have symptoms for weeks or months while others will become ill in a matter of days.
"It can be a challenging diagnosis to make," she said.
Langford has been one of Cosner's doctors in Cleveland. Cosner travels there every three to five months for surgeries to treat complications in his lungs that have resulted from the disease.
Because of the nature of Wegener's, some of its treatments are similar to those used for cancer patients.
"We think the immune system is overactive, and our treatment is geared toward trying to address this," said Langford.
Treatment typically includes smaller doses of chemotherapy drugs (given orally, rather than injected) designed to reduce the immune response.
In some cases, a patient who has been on drugs for a while can be taken off them, but they are carefully monitored while in this state which is known as remission.
However, Wegener's is not cancer.
"I always am pretty careful to point that out to patients," said Langford.
Wegener's is also generally treatable. While once a fatal disease that killed most patients in five to six months, most patients will respond to treatment.
But they do need monitoring.
"People can have complications as a result of their treatment," said Langford. "Because all of these suppress the immune system…there can be infections."
But while the outlook has improved for these patients, Langford notes that many aspects--such as how the disease originates and how it progresses from inflamed blood vessels to problems with the kidneys and lungs and many other areas the blood vessels reach--remain unknown.
"We've come a long way with this illness, but there's a lot we have left to learn," said Langford.
For most people, a cold is a cold.
"Colds go away, so with a cold you should not have arthritis," said Hellmann. "Colds do not cause you to cough up blood or cause you to become noticeably short of breath."
"Most colds get better within a week," he said.
But he added that, "anything that lasts more than a week or two should be looked at."
And Cosner wants people who may have the same disease he has to know about it.
"WG is something that's totally not well known," he said. "Mostly, everybody that I've talked to was misdiagnosed."
But while he doesn't blame his own doctors for the disease, he would like others to be aware of it.
"That's just part of the game, and I just really want to spread knowledge about that," said Cosner.
Sara Loeffelholz contributed to this report.