Almost certainly! However the size of this problem may be small or at least is getting smaller.
You may recall my previous post on the history of MS that MS was first described as a disease by the great French neurologist Charcot. Charcot was the first to describe the clinical features in combination with the pathological features of MS at post-mortem. This is the so called “clinicopathological correlate” and is the conventional way of describing a disease in medicine.
(One of the reasons I am taking so much flak for my stance on CCSVI; is that it does not conform to a conventional definition of a disease at the present time.)
As you are aware we cannot apply the conventional definition of MS clinically; it is simply not practical, and too dangerous, to do a biopsy of the brain or spinal cord to confirm the diagnosis of MS. For some diseases, for example brain tumours, the vast majority require a biopsy to make a diagnosis.
Back to MS: we know from post-mortem studies that neurologists are not 100% accurate in making a diagnosis. Unfortunately, we get it wrong about 5% of the time. In other words 1 out of every 20 people who die with a diagnosis of MS have a different disease at post-mortem. You may find this very surprising but MSologists are better than other neurological subspecialties. With Parkinson’s and Alzheimer’s disease neurologists get the diagnosis wrong in up to 20% of cases.
As new diseases that mimic MS get they get excluded from pool of cases that get diagnosed as being MS. Two classic examples of this are:
1. Optic-spinal MS: this is a relatively rare form of MS that is most common in Asia and Japan. The majority of these cases now have a specific antibody that can be detected in their blood that labels them as having a disease that we call neuromyelitis optica or NMO.
2. Tropical spastic paraparesis or HTLV1-associated myelopathy. This disease mimics primary progressive MS and is due to a virus that is distantly related to the HIV virus. Prior to us knowing that this disease was caused by HLTV1 people presenting with this disease in Europe were frequently diagnosed as having MS.
So yes, there may be other MS mimics to be found that in the future will be labelled as being another disease.
Additional reading:
HTLV1-associated myelopathy or tropical spastic paraparesis,
neuromyelitis optica or NMO