Blood Testing for Multiple Sclerosis
What is multiple sclerosis / MS?
Multiple sclerosis is a progressive autoimmune disease of the central nervous system; i.e., it is a disease in which a person's own immune system attacks their nervous system. The autoimmune attack results in demyelination: removal of the insulating sheath surround nerve fibres. The disease is more common in women and onset tends to be in young adulthood.
What causes MS?
The etiology of MS still remains very uncertain. It is most likely that the disease is caused by some combination of environmental and genetic factors. The idea that MS has some kind of genetic basis is supported by the fact that relatives of sufferers are more likely to develop the disease, particularly if they are first degree relatives. It is probably a polygenic disease, and some genes have already been linked to an increased likelihood of development. Some such genes are the human leukocyte antigen system, which produce the MHC (major histocompatability complex - an antigen recognition site present on leukocytes).
There are also proposals that exposure to infectious pathogens could play a role in tendency to develop MS. There is some argument that exposure to different pathogens early in life provides some protection against multiple sclerosis; this is termed the hygiene hypothesis. The prevalence hypothesis postulates that a widespread pathogen that is a common sub-clinical infection could lie dormant for many years, later causing the activation of the immune system against the self.
There is some evidence supporting the theory that viruses could be the cause of MS. The one most commonly linked to MS is the Epstein-Barr virus (EBV), although varicella zoster and human herpesvirus are also often detected in patients with multiple sclerosis.
Environmental causes may include reduced sunlight exposure, and consequently vitamin D (MS is more common in regions further from the equator), stress, low levels of uric acid, and smoking.
What are the signs and symptoms?
As multiple sclerosis is a non-selective demyelinating disease, almost any neurological symptom can be seen. Often patients will have a clinically isolated symptom (CIS) months before they first seek medical attention. This CIS may be of a visual, sensory, motor, or cerebellar nature. Only 30-70% of patients that experience a CIS will develop multiple sclerosis. Patients do not normally present and receive diagnosis until they are showing multiple signs; these could be muscle weaknesses, changes in sensation, ataxia, optic neuritis, double vision, nystagmus, fatigue, bladder and bowel problems, changes in mood, cognitive impairment, difficulty in swallowing and speaking, and many more.
New research for clinical biomarkers
Until recently, it has been very difficult to definitively diagnose and assess the course of multiple sclerosis in a patient. However, work by Clinical Research Fellow Dr Rachel Farrell (Institute of Neurology, UCL) has uncovered a potential new biomarker for MS. The marker is derived from infection with Epstein-Barr virus, which results in expression of the immunoglobulin anti-EBNA1-IgG. Levels of this anti-EBNA1-IgG can be measured and used to diagnose and chart the course of a patient's disease. For the first time, this may enable doctors to predict the progression of a patient's disabiliity, allowing the patient to prepare themselves for the future.
Biomarkers have been a concentrated area of research for years, but this is the first time that a possible candidate has been discovered.
This article was originally published on the TJC Global Blog.