Legislators sometimes serve Minnesotans in unexpected ways. Take Rep. Sheldon Johnson. The nine-term DFLer from St. Paul’s East Side is serving this summer in a way he never thought he would. He’s speaking out about a misunderstood and wicked disorder, Lyme disease.

Johnson, 64, is a retired corrections worker and a quietly diligent legislator who started thinking last year that this term would be his last. The decision was sealed in November when first one, then the other of his knees inexplicably and painfully swelled so badly that he could not walk.

The Lyme disease diagnosis was a surprise, but it made sense. Lyme disease is a bacterial infection that’s spread by deer ticks. Those little biters can be found in all 87 Minnesota counties, but they are particularly prevalent in wooded areas populated with deer, rodents and ground-feeding birds. Johnson lives near such an area in St. Paul’s Highwood neighborhood and spends a lot of active time outdoors.

Tests determined that Johnson was likely unknowingly infected three or four years ago. That means the bacteria had ample time to spread through his body and do their dirty work. His was an advanced case.

But three weeks of daily intravenous antibiotic therapy seemed — at first — to restore Johnson to health, or at least to mobility. He looked forward to serving his last year as lead DFLer on the House committee overseeing state government agency budgets. It’s a demanding role that he enjoyed. That’s why he was puzzled by the anxiety, “brain fog,” body aches and extreme fatigue he began experiencing during the run-up to the session’s Feb. 20 start.

Before long, “my emotions were in turmoil,” Johnson recalls. He was exhausted yet slept poorly. Suicidal thoughts crossed his mind. His primary care physician prescribed anti-anxiety medication. It made him feel worse, he said.

DFL caucus researcher Jim Gelbmann recalls being shocked at Johnson’s gaunt appearance at the start of the session. The slender man had lost 30 pounds. He came to the Capitol for a few weeks. On March 6, Gelbmann said, Johnson conceded that he could not carry on. “I don’t know if I’ve ever seen anyone in such pain,” Gelbmann recalls.

Soon thereafter, Johnson found a doctor who specializes in Lyme disease treatment, Dr. Laurie Radovsky of Birch Tree Healing Arts in St. Paul. She diagnosed his symptoms as a further manifestation of Lyme disease and started him on a second course of antibiotics. Later, physical therapy was also prescribed.

He responded more slowly to treatment this time. Johnson tried to keep up with the Legislature and his constituents’ needs from home, but he was unable to return to the Capitol — not even to deliver one of the farewell speeches right after the session’s final gavel falls that have become a valued tradition for retiring legislators. It wasn’t until mid-June that Johnson said he felt “measurable improvement.” He’s better, but his symptoms have not fully abated.

With regained strength and spirit came an impulse I’ve often seen among Minnesota’s elected officials. Johnson wanted to go public with his personal story. He considers doing so almost a duty, both of his office and of citizenship. That’s a sentiment rooted in a deep — and, I hasten to add, bipartisan — faith in something fundamental to democracy: the power of an informed citizenry. (The same idea keeps a lot of journalists going, too.)

Johnson believes Minnesotans will be better armed against a mean disease if they know about his experience with it. He invited me to meet him at Dr. Radovsky’s office so she could help him convey information he thinks Minnesotans should know:

•Lyme disease is becoming more prevalent, but how much more is hard to say because it is difficult to diagnose. The state Department of Health acknowledged as much when it reported 1,305 confirmed cases in Minnesota in 2016 and 821 “probable cases” that physicians reported despite a lack of definitive clinical confirmation.

•One need not see a rash to be infected. Radovsky said many of her patients had no awareness they had been bitten by a tick.

•Mistaken diagnoses are common. Many people have been treated for disorders such as chronic fatigue syndrome, fibromyalgia or Parkinson’s disease when Lyme is the real culprit. The disease’s symptoms are highly variable and lab tests are not always conclusive.

•The disease is treatable, but advanced cases such as Johnson’s are not well understood, Radovsky said. People who have been treated for Lyme in the past should know that disease-related symptoms can recur well after an initial round of antibiotics appears to knock out the infection.

•More information and support for those afflicted can be found at the Minnesota Lyme Association, www.mnlyme.org.

Though a contest to succeed him is well underway in District 67B, Johnson is still talking like a legislator. “We should put more money into combating Lyme disease, both research and public education,” he said.

Among legislators, a pattern often prevails. The personal becomes public, and the public becomes policy. In this case, may it be so.

Lori Sturdevant is a Star Tribune editorial writer and columnist. She is at lsturdevant@startribune.com.