Intrathecal IgM as a Prognostic Marker in Multiple Sclerosis

One of the great challenges related to multiple sclerosis (MS) research is the identification of markers of prognosis and treatment response. In the last couple of decades, an association between intrathecally produced immunoglobulin M (IgM) and a more severe course of the disease has been suggested. Therefore, the objective of this literature review was to gather and review evidence from studies on intrathecally produced IgM as a prognostic marker of clinically isolated syndrome (CIS) converting to clinically definite MS (CDMS), the prognosis of MS and treatment response in patients with MS. This was accomplished through a systematic literature search of the PubMed database, which resulted in 719 hits that were then systematically assessed with well-defined inclusion and exclusion criteria. This process resulted in 29 relevant research articles. The combined evidence from the current literature suggests that intrathecal IgM is a negative prognostic marker that identifies patients with CIS who have a higher risk of converting to CDMS and patients with relapsing–remitting MS (RRMS) with a higher risk of a more aggressive disease course. However, a few studies, some with large studied populations, have reported conflicting results regarding MS prognosis. Further research is needed to establish a more accurate estimate of the effect of intrathecal IgM on the disease course of MS. Further research is also necessary to evaluate the potential prognostic value of intrathecal IgM in treatment response.