Lymphopenia and DMTs for relapsing forms of MS

Abstract

Purpose of review To provide neurologists with an update on the proposed mechanisms of action (MOAs) of disease-modifying therapies (DMTs) for the treatment of relapsing MS, and their effect on peripheral blood leukocytes, in order to inform treatment decisions. Recent findings DMTs have vastly differing MOAs, including effects on peripheral blood leukocyte counts, particularly lymphocytes. The clinical implications of changes in lymphocyte counts need to be understood in the context of the underlying MOAs of each respective DMT, with treatment tailored to individual patient needs. Summary DMTs can alter lymphocyte counts, subsets, activation, and distribution , and thus can influence immune surveillance. Serial monitoring of total leukocytes and absolute lymphocyte counts (ALCs) is advisable in patients receiving DMTs. ALCs should be interpreted regarding expected immu-nologic changes and individual patient characteristics. Any decision to switch DMTs should consider these factors, along with drug efficacy, safety, and effect on quality of life. MS is a chronic, immune-mediated, demyelinating CNS disorder 1 associated with development of neurologic deficits and subsequent accumulation of physical and cognitive disability. 2 Around 2.3 million people worldwide and 400,000 in the USA have MS, 3 with a higher incidence in women. 4 Although there are regional variations, the prevalence of MS in the US in 2012 was 149.2 per 100,000 individuals. 4 Relapsing forms of MS (RMS) account for over 80% of all MS cases at onset, and thus comprise a substantial proportion of MS cases under a neurologist's care. 1