Psoriasis comorbidity affects multiple sclerosis neurological progression: a retrospective case – control analysis

Background: Multiple sclerosis (MS) and psoriasis are inflammatory disorders, with epidemiological and biological associations. The impact of one disease on the course of the other has not been studied. Objective: To characterize patients with psoriasis and MS, and to assess whether psoriasis comorbidity affected the progression of MS. Methods: A retrospective case–control study. Patients with psoriasis comorbidity were identified from 3456 patients included in the Sheba Hospital Multiple Sclerosis Center database. Clinical and demographical characteristics and MS progression-related outcomes in patients whose follow-up exceeded 5 years were analysed and compared to those of a matched control cohort of MS-only (MSO) patients. Results: Forty-five (1.3%) MS patients had psoriasis comorbidity. Psoriasis preceded MS in 35 (78%) cases. The psoriasis was defined as mild, moderate and severe in 24 (53%), twelve (27%) and nine (20%) cases respectively. MS progression-related outcomes were evaluated in 35 patients that had follow-up over 5 years. Patients with psoriasis onset preceding relapsing-remitting MS (RRMS) had slower progression of disease compared to MSO patients, as manifested by a longer time to second relapse (P < 0.01) and a longer time to significant neurological disability scores (P < 0.03). Conclusion: Psoriasis comorbidity preceding the onset of MS is associated with slower progression of disability.