The presence of multiple sclerosis (MS) lesions which are surrounded by a rim of iron (IRL) is suggested to signify a more severe disease course. These IRLs can be detected on ultra-high field strength brain MRI like 7-T or 3-T. Studies with large MS patient cohorts have demonstrated that IRLs are particularly frequent in progressive MS subtypes. So far only small longitudinal MRI and clinical cohorts have reported the evolution of IRLs many years after their initial formation, as well as their link to clinical disability or disease progression.

The formation of IRLs is not uniform across MS cohorts so identifying risk factors which predispose individuals to them may provide a useful biomarker for clinical progression. One set of risk factors include genetic variants which prevent some MS patients from resolving the inflammation present at the start of their disease onset. Recent genetic studies of MS are beginning to implicate microglia (inflammatory/immune cells) in MS pathogenesis. Certain genetic variants change the activation states of certain cell populations like microglia and astrocytes which governs their response to CNS damage. It is not known how this genetic variation contributes to the formation, persistence and accrual of IRLs, warranting genotyping studies.

This study relies on the recruitment of participants who received a susceptibility-based brain MRI between 2008-2012, this cohort of patients will be identified to the research team by the clinical team. To minimise inconvenience these patients will be sent a patient information sheet at least 2 weeks ahead of their scheduled annual appointment and will be contacted 2 days before their appointment to confirm whether they are interested in participating. If they agree, they will be asked to attend clinic 45 minutes before their scheduled time so there is sufficient time to meet the research team, discuss any questions and if willing, consent. As this study comprises a cross-sectional genetics component and a longitudinal MRI cohort, patients are able to consent to either/both the provision of blood samples and/or an additional susceptibility-based brain MRI. If the participant consents to provide blood samples they will be taken on the same day and stored in a -80'C freezer. When the total samples being stored reaches the target of 100 participant samples they will be shipped for analysis at Johns Hopkins University in the United States where funding has been secured to perform the genotyping studies. The research team will also collect additional clinical and demographic data from the already available medical records which will be anonymously shared with Johns Hopkins University.

Participants may also consent to receive an MRI as part of the longitudinal MRI cohort component. This will be split into two phases, the first phase has already secured funding for 30 participants to receive an MRI. Of the participants who have consented to receive an MRI, initially 30 will be invited to the Sir Peter Mansfield Imaging Center where they will meet a member of the research team and undergo the scan. Additional clinical and demographic information will also be collected at this visit. Following completion of phase 1 and after securing additional funds, more patients who have consented to receive the MRI will be invited to the SPMIC to receive the scan, the exact number of patients will be determined from analysis of the pilot data.