CHICAGO—Investigators have found evidence of a unique antibody for a mysterious neuropathy affecting pork manufacturing plant workers in the Midwest, a Mayo Clinic neurologist reported April 16 here at a news briefing at the AAN annual meeting.
The illness, classified as an immune polyradiculoneuropathy and also referred to as “progressive inflammatory neuropathy,” has been diagnosed in nine women and nine men since it was first recognized in November 2006. All worked at the Quality Pork Processors plant in Austin, MN. Since then, five similar cases were identified at an Indiana plant, and one similar case was encountered at a Nebraska plant.
All of those affected worked in or near an area where compressed air was used to extract pig brains, said Daniel Lachance, MD, a neurologist at the Mayo Clinic in Rochester, MN, who has been studying the disease and treating patients. “With the individuals working in the same place presumably having exposure to aerosolized brain tissue, we're thinking there may somehow be an immune response to this trigger that therefore is translated to the neurological illness,” Dr. Lachance said. “We do not yet understand the precise mechanism by which this occurs.”
James Sejvar, MD, a neurologist and epidemiologist from the Centers for Disease Control and Prevention, heads the CDC's role in the investigation. He said the workers wore gloves and cloaks but did not have a “significant amount of respiratory protection.”
Dr. Lachance said he and other Mayo Clinic researchers have discovered a unique pattern of antibodies in patients. “We have not identified a name for this, but in the Mayo Clinic experience where thousands of sera are examined yearly, we have never seen this pattern before in any other patient group,” he said.
Dr. Lachance explained that this pattern is visible on an immunofluorescent assay. “I'm talking about a visual correlate of antibody binding to these tissues. It doesn't imply there are more than one [antibody] — we don't even know how many there are.”
The investigation started this past November, when the Minnesota Department of Health received reports of illness stemming from the Austin plant. Neurology Today covered the developing story in February.
Manifestations range from transverse myelitis and inflammation of the spinal cord in one patient to mild weakness, fatigue, numbness, and tingling in arms and legs in several others. “Pain seems to be a very common compliant,” Dr. Lachance said. “Almost all have disturbance of sensory function.”
None of the patients have completely recovered, he added; all have either improved or stabilized, and some have even relapsed.
Dr. Lachance said he hopes that any discoveries about this disease will add to understanding of autoimmunity. “There are several syndromes that are hypothesized to be the result of autoimmunity but in most cases we don't know the trigger. But in this case it being somewhat circumscribed and an almost human experiment of nature, so we may have the opportunity to understand how an antigen can be presented and how a body's immune system can react to produce disease.”
The CDC is asking neurologists to report any cases of neuropathy among patients who have been exposed to pig butchering or processing during the past year. To contact the CDC, call 770-488-7100. •