Delayed diagnosis of multiple sclerosis in males: may account for and dispel common understandings of different MS ‘types’

Multiple sclerosis (MS) is a long-term neurodegenerative condition that affects functioning of the central nervous system, and estimates of its prevalence range from 1–2.5 million people diagnosed worldwide.1,2 Just as the central nervous system mediates a breadth of bodily functions, MS can manifest in varied ways, often leading to confusion as to whether ill-health is caused by MS or something else. MS trajectories vary between individuals, and different MS ‘types’ are commonly used to describe patterns. Relapsing remitting MS (RRMS) refers to short-term exacerbations (relapses) and recovery (remission); secondary progressive MS (SPMS) develops after RRMS and describes long-term permanent neurodegeneration. Primary progressive MS (PPMS) also refers to long-term permanent neurodegeneration, but without a relapsing remitting stage preceding it.3 Although these different MS ‘types’ are commonly referred to within professional and lay circles, individuals’ trajectories do not always fit comfortably into their descriptions,4 no biomarkers have been identified to distinguish between them,5 and they are not recognised as subtypes in the World Health Organization’s International Statistical Classification of Diseases and Related Health Problems 10th Revision (ICD-10).6 Internationally MS appears to be more prevalent in females than males1,7 and the difference in ratio seems to be rising,8 except in the case of PPMS, where those diagnosed are more likely to be male and older.9 Previous research indicates no clear cause for apparent sex …