Highly active multiple sclerosis: An update.

Multiple sclerosis (MS) is the most prevalent chronic inflammatory disease of the central nervous system (CNS), affecting more than 2 million people worldwide. It is characterized by brain and spinal cord involvement. There are the relapsing remitting MS (RRMS), primary progressive MS (PPMS), and secondary progressive MS (SPMS) phenotypes. There is a subgroup of RRMS patients who have a more aggressive disease course marked by a rapid accumulation of physical and cognitive deficit, despite treatment with 1 or more disease modifying drugs (DMTs). In the past, this disease phenotype was called "aggressive" MS (AMS); it is now called highly active MS (HAMS). It is generally agreed that the severe nature of this phenotype requires different treatment decisions. Unfortunately, there is no consensus on the definition of AMS or the treatment algorithm. In this article we review HAMS in relation to its definition and the treatments available.