Sjögren's syndrome: An underdiagnosed condition in mixed connective tissue disease

OBJECTIVE: To determine the prevalence of sicca symptoms, dry eye, and secondary Sjögren's syndrome and to evaluate the severity of dry eye in patients with mixed connective tissue disease. METHODS: In total, 44 consecutive patients with mixed connective tissue disease (Kasukawa's criteria) and 41 healthy controls underwent Schirmer's test, a tear film breakup time test, and ocular surface staining to investigate dry eye. In addition, the dry eye severity was graded. Ocular and oral symptoms were assessed using a structured questionnaire. Salivary gland scintigraphy was performed in all patients. Classification of secondary Sjögren's syndrome was assessed according to the American-European Consensus Group criteria. RESULTS: The patients and controls had comparable ages (44.7±12.4 vs. 47.2±12.2 years) and frequencies of female gender (93 vs. 95%) and Caucasian ethnicity (71.4 vs. 85%). Ocular symptoms (47.7 vs. 24.4%) and oral symptoms (52.3 vs. 9.7%) were significantly more frequent in patients than in controls. Fourteen (31.8%) patients fulfilled Sjögren's syndrome criteria, seven of whom (50%) did not have this diagnosis prior to study inclusion. A further comparison of patients with mixed connective tissue disease with or without Sjögren's syndrome revealed that the former presented significantly lower frequencies of polyarthritis and cutaneous involvement than did the patients without Sjögren's syndrome. Moderate to severe dry eye was found in 13 of 14 patients with mixed connective tissue disease and Sjögren's syndrome (92.8%). CONCLUSIONS: Sjögren's syndrome, particularly with moderate to severe dry eye, is frequent in patients with mixed connective tissue disease. These findings alert the physician regarding the importance of the appropriate diagnosis of this syndrome in such patients.