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.