Patients with progressive multiple sclerosis (MS) appear to have a greater susceptibility to infection than patients with relapse-remitting MS, according to a recently published study in Multiple Sclerosis and Related Disorders.

It is widely recognized that patients with MS are more likely to suffer from heart, respiratory, autoimmune, and metabolic diseases. These comorbidities are known to lead to worse outcomes. 

Evidence indicates that patients with MS are also more prone to severe infections than the common population. Although the relationship between disease-modifying therapies and severe infection has already been studied by several authors, there is currently scarce literature regarding the impact of other factors, such as MS phenotype, in the risk of infection. 

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Therefore, the authors aimed to compare the incidence of severe infections in MS with different phenotypes, namely primary progressive MS, secondary progressive MS, and relapse remitting MS. Severe infection was defined as hospitalization in which the primary inpatient diagnosis was an infection.

The retrospective analysis of claims data included over 4500 patients with MS, of which over 2000 had relapse remitting MS, 1000 unspecified MS, and 800 primary or secondary progressive MS. The overall length of follow-up was 3.7 years. Close to 7% of the included patients died during the course of the study.

Results revealed that the risk of severe infection was significantly higher in the primary progressive MS and secondary progressive MS cohorts. Urinary tract infections and respiratory tract infections were the most common ones in both groups. 

Patients with progressive MS were also more likely to suffer from cardiovascular comorbidity, with urinary tract disorders and depression being the most common comorbidities. Interestingly, disease-modifying therapies were considerably more frequent among patients with relapse-remitting MS.

Regarding age and sex, infection rates were higher in older patients.

“This study provides new evidence to understand factors modulating clinical susceptibility to infections in people with MS,” the authors wrote.


Knapp R, Hardtstock F, Krieger J, et al. Serious infections in patients with relapsing and progressive forms of multiple sclerosis: a German claims data study. Mult Scler Relat Disord. Published online October 15, 2022. doi:10.1016/j.msard.2022.104245