Coexistence of Multiple Sclerosis and Alzheimer's disease: A review

Background: People with multiple sclerosis (MS) are living longer than ever and will likely face the same age-related diseases as other seniors; however, there is strikingly little information on the coexistence of MS with many common diseases of aging. In particular, little appears to be known about the coexistence of MS with Alzheimer's disease (AD), the most common form of dementia. Methods: In this review, we explore what is known about the coexistence of MS and AD, including a focused literature search to identify any reports of individuals with both MS and AD (PubMed, to May 2017). We also discuss the wider epidemiology, diagnosis, and pathophysiology of MS and AD. Results: In total, we found 24 individuals with pathological features of both MS and AD described as case series or reports (published between 1976-2014), but no epidemiological or population-based studies, aside from one conference proceeding (2011). Comorbid MS and AD was reported in a broad range of MS disease courses including relapsing-remitting, primary progressive, secondary progressive and so-called 'benign.' Despite the clear diagnostic challenges involved, these individual case reports provide evidence that AD and MS can coexist in the same person. Conclusion: In summary, we highlight a major knowledge gap in our understanding of two potentially common neurological conditions. With the ageing population, and an estimated 2.3 million people living with MS and 46 million with AD or other dementias worldwide, it will become increasingly important to recognize and understand how to manage individuals with these complex comorbid conditions.