While salivary gland ultrasound (SGU) has gained prominence for evaluating Sjögren's syndrome, little information exists on SGU appearance of sarcoidosis and amyloidosis, potential mimics of Sjögren's syndrome. Our goal in this study was to estimate the diagnostic accuracy of major SGU features in differentiating Sjögren's syndrome from sarcoidosis, amyloidosis, and controls.
We enrolled consecutive adult ambulatory patients with a clinical diagnosis of Sjögren's syndrome fulfilling the 2016 American College of Rheumatology (ACR) classification criteria; we also enrolled patients with a clinical diagnosis of sarcoidosis or systemic immunoglobulin light chain (AL) amyloidosis, with histologic confirmation from any tissue, and rheumatology outpatients without diagnoses affecting salivary glands. Subjects underwent major SGU using the Hočevar protocol, with resulting video clips reviewed blind to clinical diagnosis.
Sjögren's syndrome SGU scores were greater than in patients from the other groups, but there were no distinguishing salivary gland features from AL amyloidosis or sarcoidosis. None of the patients in the control group scored higher than 17, a cutoff previously suggested for Sjögren's syndrome, but 27% of patients with AL amyloidosis and 19% with sarcoidosis scored higher than 17. Adding Hočevar SGU scores of ≥17 to the 2016 ACR/European League Against Rheumatism criteria in a parallel scheme increased the sensitivity for Sjögren's syndrome from 87% to 98%, while combining the 2 criteria in series increased specificity from 81% to 98%.
Sjögren's syndrome, sarcoidosis, and AL amyloidosis share common SGU features that can help distinguish these conditions from patients without systemic rheumatologic disease. Clinicians should carefully consider these potential mimics when interpreting salivary gland US results.