Recent items in The ALS Digest, an online publication, have suggested that the tick-borne, bacterial infection known as Lyme disease can mimic ALS and that new tests can tell the difference between these conditions with certainty.
But can this infectious disease actually be confused with ALS? And, if you do get a positive result on a Lyme test, can you be assured you don’t have ALS?
Not likely, experts say.
ALS involves dysfunction of upper motor neurons (the nerve cells that run from the brain to the spinal cord) and lower motor neurons (the nerve cells that go to muscles). This dysfunction is detected by physical exam and electrical testing.
"The selective involvement of upper and lower motor neurons, sparing other nervous system structures, is the hallmark of ALS," says neurologist David Chad, who directs the MDA clinic at the University of Massachusetts in Worcester, in the heart of Lyme disease country. "That’s not typical of the neurological complications of Lyme disease."
A red rash with a clear center, resembling a "bull’s eye," is common with Lyme disease. It has a set of symptoms different from those of ALS.
Lyme, Chad notes, "has the tempo of an infectious disease. Although there are chronic forms, Lyme disease usually presents as an infection, with a rash, followed by fever, headache, limb pain and malaise."
In contrast, he says, ALS, in the vast majority of cases, "is painless, comes on over months, and is not accompanied by a systemic component."
Allen Steere, a rheumatologist at Massachusetts General Hospital in Boston and an expert in Lyme disease, says a new blood test for Lyme, known as the VlsE, isn’t any better than slightly older tests at detecting Lyme disease in someone who is far enough into it to have neurologic symptoms.
There are "false positive" results with Lyme disease tests, Steere says, because they aren’t completely specific for the disease. Newer tests may even show more false positives, he says, than the testing procedure now recommended by the Centers for Disease Control and Prevention.
Only once in his long career has Chad ever found it advisable to treat a patient for Lyme disease when he thought the problem was much more likely to be ALS. That, he says, was a special case, in which the Lyme disease treatment proved essential for the family’s peace of mind.