“These protein inhibitors have changed completely the face of treating inflammatory arthritis,” Dr. Shaw says. “If he’d have gotten this 15 years ago, his playing career would have been over.”

Mickelson said he plans on taking the injections for about a year, after which he believes he’ll be symptom free.

Dr. Shaw, who has not treated Mickelson, says Mickelson and his doctors will decide the best long-term treatment plan, but that in his experience, patients with PA need to stay with the treatments for the rest of their lives.

“The disease goes in and out of remission without treatment, but the disease is still there,” he says. “I think patients need chronic therapy that never stops. What he does will be between him and his doctor, but most of us keep it going chronically.”

The most common side effect of the injections is infection, Dr. Shaw says.

“The drug is playing with your immune system, lowering it ever-so-slightly, but still lowering it. So it leaves you susceptible to infections. If you get a fever, you go off [the drug for] a little while, get well and then go back on it.”

Philip Mease, MD, a practicing rheumatologist and clinical professor at the University of Washington School of Medicine in Seattle, agreed with Dr. Shaw that Mickelson probably wouldn’t be able to come off the injections anytime soon.

“I never like to use the word ‘forever,’ but for the foreseeable future, unless something new comes along and there’s a cure for it, I’d say he’ll need to be on it,” Dr. Mease says. “And even for the high-end athlete, I don’t know if he’ll be able to not have some impact from the PA, even on the Enbrel.”

Dr. Mease hopes Mickelson’s case will raise awareness of PA.

“It can elude diagnosis,” Dr. Mease says. “It typically takes a savvy dermatologist or rheumatologist to find it. It’s not always that the person even knew he or she had psoriasis. That can be misdiagnosed as eczema or not diagnosed at all.”

Even grappling with such significant health issues, Mickelson rallied in the final rounds of the PGA tournament to finish at 6-under, tying for 12th place.