Multiple sclerosis (MS) patients have been considered a higher-risk population for COVID-19 due to the high prevalence of disability and disease-modifying therapy use; however, there is little data identifying clinical characteristics of MS associated with worse COVID-19 outcomes. Therefore, we conducted a multicenter prospective cohort study looking at the outcomes of 40 MS patients with confirmed COVID-19. Severity of COVID-19 infection was based on hospital course, where a mild course was defined as the patient not requiring hospital admission, moderate severity was defined as the patient requiring hospital admission to the general floor, and most severe was defined as requiring intensive care unit admission and/or death. 19/40(47.5%) had mild courses, 15/40(37.5%) had moderate courses, and 6/40(15%) had severe courses. Patients with moderate and severe courses were significantly older than those with a mild course (57[50-63] years old and 66[58.8-69.5] years old vs 48[40-51.5] years old, P = 0.0121, P = 0.0373). There was differing prevalence of progressive MS phenotype in those with more severe courses (severe:2/6[33.3%]primary-progressing and 0/6[0%]secondaryprogressing, moderate:1/14[7.14%] and 5/14[35.7%] vs mild:0/19[0%] and 1/19[5.26%], P = 0.0075, 1 unknown). Significant disability was found in 1/19(5.26%) mild course-patients, but was in 9/15(60%, P = 0.00435) of moderate course-patients and 2/6(33.3%, P = 0.200) of severe course-patients. Diseasemodifying therapy prevalence did not differ among courses (mild:17/19[89.5%], moderate:12/15[80%] and severe:3/6[50%], P = 0.123). MS patients with more severe COVID-19 courses tended to be older, were more likely to suffer from progressive phenotype, and had a higher degree of disability. However, disease-modifying therapy use was not different among courses.

SARS-CoV-2 is the virus responsible for the ongoing COVID-19 outbreak. The virus uses ACE2 receptor for viral entry. ACE2 is part of the counter-regulatory renin-angiotensin-aldosterone system and is also expressed in the lower respiratory tract along the alveolar epithelium. There is, however, significant controversy regarding the role of ACE2 expression in COVID-19 pathogenesis. Some have argued that decreasing ACE2 expression would result in decreased susceptibility to the virus by decreasing available binding sites for SARS-CoV-2 and restricting viral entry into the cells. Others have argued that, like the pathogenesis of other viral pneumonias, including those stemming from previous severe acute respiratory syndrome (SARS) viruses, once SARS-CoV-2 binds to ACE2, it downregulates ACE2 expression. Lack of the favourable effects of ACE2 might exaggerate lung injury by a variety of mechanisms. In order to help address this controversy, we conducted a literature search and review of relevant preclinical and clinical publications pertaining to SARS-CoV-2, COVID-19, ACE2, viral pneumonia, SARS, acute respiratory distress syndrome and lung injury. Our review suggests, although controversial, that patients at increased susceptibility to COVID-19 complications may have reduced baseline ACE2, and by modulating ACE2 expression one can possibly improve COVID-19 outcomes. Herein, we elucidate why and how this potential mechanism might work.

Importance: Multiple sclerosis patients have been considered a higher-risk population for COVID-19 due to the high prevalence of disability and disease-modifying therapy use; however, no study has identified clinical characteristics of multiple sclerosis associated with worse COVID-19 outcomes. Objective: To evaluate the clinical characteristics of multiple sclerosis, including staging, degree of disability, and disease-modifying therapy use that are associated with worse outcomes from COVID-19. Design: Prospective cohort study looking at the outcomes of multiple sclerosis patients with COVID-19 between March 1st and May 18th, 2020. Setting: This is a multicenter study of three distinct hospital systems within the U.S. Participants: The study included 40 consecutive patients with nasopharyngeal/oropharyngeal PCR-confirmed COVID-19 infection. Exposures: Multiple sclerosis staging, severe disability (based on baseline-extended disability status scale equal to or greater than 6.0) and disease-modifying therapy. Main Outcomes and Measure: Severity of COVID-19 infection was based on hospital course, where a mild course was defined as the patient not requiring hospital admission, moderate severity was defined as the patient requiring hospital admission to the general floor only, and most severe was defined as requiring intensive care unit admission and/or death. Results: For the 40 patients, the median age was 52(45.5-61) years, 16/40(40%) were male, and 21/40(52.5%) were African American. 19/40(47.5%) had mild courses, 15/40(37.5%) had moderate courses, and 6/40(15%) had severe courses. Patients with moderate and severe courses were significantly older than those with a mild course (57[50-63] years old and 66[58.8-69.5] years old vs 48[40-51.5] years old, P=0.0121, P=0.0373). There was differing prevalence of progressive multiple sclerosis staging in those with more severe courses (severe:2/6[33.3%]primary-progressing and 0/6[0%]secondary-progressing, moderate:1/14[7.14%] and 5/14[35.7%] vs mild:0/19[0%] and 1/19[5.26%], P=0.0075, 1 unknown). Significant disability was found in 1/19(5.26%) mild course-patients, but was in 9/15(60%, P=0.00435) of moderate course-patients and 2/6(33.3%, P=0.200) of severe course-patients. Disease-modifying therapy prevalence did not differ among courses (mild:17/19[89.5%], moderate:12/15[80%] and severe:3/6[50%], P=0.123). Conclusions and Relevance: Multiple sclerosis patients with more severe COVID-19 courses tended to be older, were more likely to suffer from progressive staging, and had a higher degree of disability. However, disease-modifying therapy use was not different among courses.