Subjective Symptoms and Disease Activity Related to Serum Zinc Concentration in Primary Sjögren's Syndrome

Background/Objectives: We examined the frequency of zinc deficiency in patients with Sjögren's syndrome (SS) and the relationship between zinc deficiency and each of the subjective symptoms and disease activity. Methods: We enrolled 164 patients aged ≥ 20 years with primary SS (pSS) based on the revised diagnostic criteria of the Ministry of Health, Labor and Welfare (1999) and 144 patients with RA diagnosed according to the ACR/EULAR classification criteria for RA (2010) as a comparison group. Subjective symptoms were confirmed using an original questionnaire, and disease activity was determined using the European League Against Rheumatism Sjögren's Syndrome Disease Activity Index (ESSDAI). The serum zinc concentrations were measured in both SS and RA patients. Results: The rate of zinc deficiency in the SS group was 26.1%, significantly higher than that in the RA group (7.6%). The rate of zinc deficiency was significantly higher in the pSS group compared with Japanese health checkup recipients reported in the literature. The mean serum zinc concentration in primary SS was 60.6 ± 7.3 µmol/L in the high disease activity group with an ESSDAI of ≥5 points, which was significantly lower than the concentration of 69.7 ± 10.2 µmol/L in patients with an ESSDAI of ≤4 points. Conclusions: The frequency of zinc deficiency was higher in patients with pSS than in patients with RA. Disease activity was also higher in patients with zinc deficiency, suggesting an association between zinc concentration and organ involvement in pSS.