To determine the prevalence of paramagnetic rim lesions (PRLs) in African American patients with multiple sclerosis (AAwMS) compared to Caucasian (CAwMS).

In this retrospective study of 139 AAwMS and 132 CAwMS quantitative susceptibility mapping (QSM), an MRI approach sensitive to iron, was used to identify PRLs. A linear model assessed the relationship between EDSS and race, adjusting for total lesion number (TLN), sex, age and disease duration (DD). The association of PRL per patient and race was modeled, adjusting for clinical variables and total lesions, using a zero-inflated Poisson regression.

The cohorts were well matched on all clinical variables and TLN. In a linear model, AAwMS had a higher EDSS (p-value <0.001) with, on average, a 1.16-point higher EDSS (95% CI: [0.73, 1.60] than CAwMS. AAwMS had a mean of 1.3 (2.72) PRL whereas CAwMS had 0.82 (1.69), p=0.085. In the zero-inflated Poisson model, the log odds ratio of having no PRL was 0.53 (95% CI: [0.29, 0.97], p-value = 0.039) for AAwMS, indicating more patients have at least one PRL. In the Poisson model, only TLN (p = 0.021) and gender (p = 0.046) were found to be significant, which indicates that AAwMS were more likely to have one PRL, however among all patients with PRL, the total number of PRL did not depend on race.  

This is the first study to explore racial differences in the occurrence of chronic active lesions and provides preliminary evidence that PRL could relate to racial specific differences in disease pathology, an area which has been significantly understudied.