Can Sjögren's Syndrome Cause Decreased DLCO?
Yes, Sjögren's syndrome commonly causes decreased DLCO, with reduction occurring in up to 81.8% of patients, making it one of the most frequent pulmonary function abnormalities in this disease. 1
Prevalence and Significance of DLCO Reduction
- DLCO reduction is the predominant pulmonary function abnormality in Sjögren's syndrome, occurring even when spirometry remains normal. 2
- Research demonstrates that 81.8% of primary Sjögren's syndrome patients show reduced DLCO, with 45.5% having mild deficits and 36% having moderate deficits. 2
- The reduction in DLCO often represents early emphysematous changes or interstitial lung disease (ILD) before spirometric abnormalities or significant respiratory symptoms develop. 2
Disease Severity Stratification Using DLCO
The 2021 Chest consensus guidelines establish DLCO as a critical parameter for staging Sjögren's-ILD severity: 1
- Moderate disease activity: DLCO between 40% and 70% predicted
- Severe/high disease activity: DLCO < 40% predicted
Mechanisms of DLCO Reduction
DLCO reduction in Sjögren's syndrome results from multiple pulmonary manifestations: 2, 3
- Interstitial lung disease (ILD) occurs in 9-30% of patients and is the primary cause of DLCO reduction, with nonspecific interstitial pneumonia being the most common pattern. 1, 3
- Emphysematous changes are found in up to 94.5% of patients and may represent early pulmonary involvement even before ILD becomes apparent. 2
- Diffuse lymphocytic infiltration of airways and small airways disease contribute to gas exchange abnormalities. 3
Clinical Implications and Monitoring
Baseline DLCO measurement is mandatory for all Sjögren's patients with suspected or established ILD, with initial follow-up testing every 3-6 months for at least 1-2 years. 1
- DLCO correlates with disease severity and mortality risk in Sjögren's-ILD patients. 4, 5
- Patients with extraglandular Sjögren's syndrome show significantly lower DLCO compared to controls and even compared to scleroderma patients. 4
- DLCO impairment correlates with the presence of cryoglobulins and low complement levels, suggesting immune complex deposition as a mechanism. 4
Important Clinical Pitfalls
- Discordance between PFT abnormalities, symptoms, and HRCT findings commonly occurs in Sjögren's syndrome, so DLCO reduction may be present despite minimal symptoms or normal chest imaging. 1
- DLCO reduction can occur with normal spirometry in 95.4% of patients, making it a more sensitive marker than dynamic lung volumes for early pulmonary involvement. 2
- The presence of reduced DLCO should prompt HRCT evaluation to characterize the pattern of lung involvement and guide treatment decisions. 1