  To assess the frequency of clinical features of Sjogren's syndrome (SS) in patients with multiple sclerosis (MS) receiving treatment with disease-modifying drugs (DMDs) or naïve to treatment and the possible association with clinical, cerebrospinal fluid (CSF) and magnetic resonance imaging (MRI) parameters.
  A multicentre cross-sectional observational study was designed, based on a structured neurologist-administered questionnaire to 440 patients.
  Twenty-eight of 230 (12%) patients receiving treatment with DMDs (DMDs(+)) and 14 of 210 (6.6%) treatment-naïve patients (DMDs(-) ) showed clinical features of SS. Four primary SS were diagnosed, two of which were DMDs(+) and two were DMDs(-) . Sicca symptoms were significantly associated with higher EDSS scores (P = 0.018), a low frequency of gadolinium-enhanced MRI-positive lesions (P = 0.018) and cerebral disturbances (P = 0.001).
Screening for the clinical features of SS should be performed in patients with MS both receiving treatment with immunomodulatory drugs and without therapy.