SHEBOYGAN, Wisc. — Phil Mickelson's recent onset of psoriatic arthritis, which he disclosed in his press conference at the 92nd PGA Championship at Whistling Straits on Tuesday, could be worse than he let on, according to the New York Times.Mickelson began having aches and intense pains five days before the U.S. Open, and at one point couldn't walk. Although Mickelson said he now feels fine, has been working out, and has even become a vegetarian, his sudden onset of conditions in June now seems to explain his lackluster golf of late.After making the cut but doing little else at the British Open at St. Andrews in July, Mickelson flew to Minnesota, where doctors at the Mayo Clinic diagnosed his condition. He was put on a medication called Enbrel, which he injects once a week, and began feeling better. The drug is meant to lower a patient's immune system and thereby stop it from attacking the body's joints."I'm no expert, but I've got the best kind that you can possibly have, and it's very treatable," Mickelson said Tuesday of the autoimmune disorder. "This has put it in remission; I'll probably take this drug for about a year, and feel a hundred percent. I'll stop it and see if it goes into remission and it may never come back. It may be gone forever."The Times story, however, suggests Mickelson may well be stuck with the disease. Christopher T. Ritchlin, an expert on psoriatic arthritis, says it's generally a lifelong affliction."Generally, it's not a disease that you take medication for a year and you stop and things are hunky-dory," Ritchlin told the Times.The Times story also extensively quoted Bob Murphy, a former PGA Tour pro whose psoriatic arthritis became too much to bear, eventually sending him toward a career in broadcasting golf for NBC."He's going to have a rough time," Murphy told the Times. "I feel for him."