JACKSON, Miss.—When he was a long-haul truck driver, Roger Hollenbaugh of Bandera, Texas, used to pass a field of “fainting goats.”

The breed falls over when startled, and Hollenbaugh couldn’t resist honking his horn and laughing as the goats swooned in unison.

Now he wonders if he might be paying some dues for that devilry.

Today, anything that catches Hollenbaugh unaware—from a loud rap on his door to an unexpected hand on his shoulder—sends the 36-year-old toppling to the ground like a felled tree. It’s one of the more bizarre symptoms of Stiff Person Syndrome, a disease his doctor calls “rarer than hen’s teeth.”

“I’ve only seen one other case, and that was when I was doing my residency,” said Dr. Michael Winkelmann, a physician at Methodist Rehabilitation Center in Jackson, Mississippi, who helped put a name to Hollenbaugh’s devastating illness.

“If it hadn’t been for him, who knows what would have happened to me,” says Hollenbaugh. “Every other doctor I went to would just give me pain pills and tell me it’s all in my head. He was interested in what was wrong with me.”

Winkelmann met Hollenbaugh in 2001. At the time, Hollenbaugh was living in Laurel, Mississippi, and was at Methodist to see someone in the hospital’s stroke unit. While Hollenbaugh visited with his friend, Winkelmann said he couldn’t help but notice the trucker’s stiff, Tin Man-like posture.

“He had extreme spasticity and his reflexes were exquisitely brisk,” said Winkelmann, who specializes in rehabilitation medicine. “That indicated something was going on at the level of the spinal cord in the brain.”

At Winkelmann’s urging, Hollenbaugh went to Methodist’s Center for Neuroscience and Neurological Recovery, where he underwent a battery of tests to examine his muscle and nerve function.

Dr. Art Leis, a neurologist and senior scientist at the center, said the tests revealed that the muscles in Hollenbaugh’s abdomen and back were constantly firing. He was like a revved engine that couldn’t return to idle.

Discovered in the ‘50s, Stiff Person Syndrome is thought to be an autoimmune disorder. “We don’t know what the trigger is,” Leis said. People who have the disease produce an antibody that interferes with the synthesis of gamma-aminobutyric acid (GABA), an amino acid that helps modulate the central nervous system.

“When you have too little GABA, there is hyper-excitability because there is nothing shutting down the nervous system,” Leis explained. “When startled, your body freezes and becomes firm like a rock and you fall like a piece of lumber. It’s very similar to the fainting goats.”

Hollenbaugh’s first symptom of the syndrome was a lack of coordination on his left side that worsened over time. He thought it might be caused by injuries sustained in 1999 while he was being treated for a migraine headache at a Texas hospital. “I was on a cardiac bed and they didn’t lock the rails and it collapsed with me on it. I hit my spine on the base and it flipped me over and I hit a cabinet and busted my head,” he said. “Several months after that I was very sick with a post-concussion. My neurologist couldn’t figure it out.”

Leis said Hollenbaugh’s condition probably went undiagnosed because doctors were relating his symptoms to his head and back injuries and treating him like a pain management case. It also didn’t help that he had a disease that many doctors have never encountered. “It’s something you might see once in a decade,” Leis said.

Once the tests at Methodist revealed the true root of Hollenbaugh’s misery, his doctors began searching the medical literature for possible treatments. They first prescribed the drug Baclofen to reduce his spasticity. When the oral doses no longer brought relief, a surgeon implanted a Baclofen pump into Hollenbaugh’s lower abdomen to deliver a higher concentration of the medication directly to his spinal cord.

“If not for the Baclofen pump I probably would have killed myself the pain was so unbearable,” Hollenbaugh said.

Hollenbaugh also has undergone several rounds of plasma pheresis, a process that removes disease-provoking components from his blood. “It’s the treatment of choice to decrease the autoimmune process,” Winkelmann said. “It reduces the body’s ability to fight itself. You’re essentially taking away the antibodies.”

As is common with people who have autoimmune disorders, Hollenbaugh’s health status has fluctuated wildly. Some days he can get around with a cane, on others he must use a wheelchair. Lately, he has suffered from double vision and struggled with his speech. And he almost died from a recent bout with pneumonia, a complication related to his inability to cough.

Through it all, Hollenbaugh has thrown his energy into sessions with Methodist’s occupational and physical therapists, trying to preserve every ability that he has left.

“We’re working on his endurance and trying to improve his gait to make it more efficient for him,” said Leigh Ann Hunt, one of Hollenbaugh’s physical therapists at Methodist. The therapy team also helped customize Hollenbaugh’s power chair to accommodate his sway back, another manifestation of the disease.

“I’m hoping I can maintain what I can so the disease doesn’t totally wipe me out,” Hollenbaugh said. “It has taken everything I used to do.”