Clinical implications for the association of psoriasis and multiple sclerosis: an observational study

Background: Multiple sclerosis (MS) and psoriasis (PsO) are distinct chronic autoimmune conditions with varying impacts on patients' lives. While the co-occurrence of MS and PsO has been reported, the underlying pathogenic link remains unclear. This study aimed to investigate the prevalence of PsO in a MS outpatient clinic population and explore the potential interplay between these conditions.

Methods: 316 MS patients who had at least one visit at our MS center in the last year, were selected from our outpatient MS Clinic electronic database and were e-mailed in August 2023 and inquired about a previous diagnosis of PsO. Demographic and MS history data were retrospectively gathered for two groups: MS patients without and with PsO. Information about MS phenotype, Expanded Disability Status Scale (EDSS) score at the diagnosis and at last follow-up, disease modifying therapy (DMT) were collected retrospectively from our MS data set. PsO diagnosis was confirmed by an experienced dermatologist and severity was assessed with the Psoriasis Area and Severity Index (PASI).

Results: Among 253 respondents, 5.85% reported a PsO diagnosis that was confirmed after the dermatological evaluation Among patients with psoriasis 66.67% had progressive course of MS (p = 0.032) and the onset of PsO typically occurred after MS diagnosis. 9 out 15 patients had a PASI score of 0 and 6 are currently undergoing treatment with an anti-CD20 therapy. Notably, a subset of our patients were on anti-CD20 therapy and did not experience a worsening of dermatological symptoms.

Discussion and conclusion: The prevalence of PsO in our outpatient MS population aligns with previous studies. Treatment approaches should be tailored to individual patient needs, emphasizing collaboration between neurologists and dermatologists. Medications like dimethyl fumarate, effective in both conditions, could be considered. The data from our study also suggest that anti-CD20 therapy may be a viable option for some patients with concurrent MS and mild PsO, without a significant worsening of dermatological symptoms. Further research is needed to elucidate the complex relationship between MS and PsO and to develop more effective therapeutic strategies for patients with both conditions.