Connective tissue disease associated interstitial pneumonia: a challenge for both rheumatologists and pulmonologists

Evaluating the diagnostic and prognostic utility of serial KL-6 measurements in connective tissue disease patients at risk for interstitial lung disease: correlations with pulmonary function tests and high-resolution computed tomography

BACKGROUND

Interstitial lung diseases associated with connective tissue diseases (CTD-ILD) necessitate reliable biomarkers for effective management. This study assesses the utility of serial Krebs von den Lungen-6 (KL-6) measurements in predicting disease activity and progression in CTD-ILD patients.

METHODS

In a prospective cohort study at a tertiary care center, 50 patients with CTD at risk of or diagnosed with ILD were enrolled. KL-6 levels and pulmonary function tests (PFTs) were measured at baseline, 6, and 12 months, alongside high-resolution computed tomography (HRCT).

RESULTS

Initial KL-6 levels were inversely correlated with PFTs, with mean values starting at 504.96 U/mL (SD ± 508.46), escalating to 739.42 U/mL (SD ± 612.75) at 6 months, and peaking at 1150.27 U/mL (SD ± 1106.70) by 12 months, reflecting disease progression. Higher KL-6 levels were consistently linked with declines in Forced Vital Capacity (FVC) (p = 0.019) and Diffusing Capacity for Carbon Monoxide (DLCO) (p < 0.001). Radiologically, increased KL-6 correlated with subpleural thickening (p = 0.003), septal thickening (p = 0.036), ground-glass opacities (p = 0.018), and other signs of advanced ILD. Sensitivity and specificity of KL-6 for detecting ILD were 86.7% and 71.4%, respectively, at a ≥ 400 U/mL threshold, improving at higher thresholds. Over the study period, patients with elevated KL-6 levels demonstrated more pronounced radiological and functional deterioration.

CONCLUSION

Serial KL-6 measurements effectively reflect disease activity and progression in CTD-ILD, with strong correlations to functional and radiological outcomes. These findings support the use of KL-6 as a valuable biomarker in the routine clinical management of these complex disorders. Our study demonstrates the significant predictive value of KL-6 for both the diagnosis and monitoring of CTD-ILD, suggesting its integration into clinical practice can enhance patient care and treatment strategies.

The Role of CX3CL1 and ADAM17 in Pathogenesis of Diffuse Parenchymal Lung Diseases

Fractalkine (CX3CL1) is a unique chemokine that functions as a chemoattractant for effector cytotoxic lymphocytes and macrophages expressing fractalkine receptor CX3CR1. CX3CL1 exists in two forms—a soluble and a membrane-bound form. The soluble CX3CL1 is released from cell membranes by proteolysis by the TNF-α-converting enzyme/disintegrin-like metalloproteinase 17 (TACE/ADAM17) and ADAM10. In this study, we evaluated the diagnostic relevance and potential roles of CX3CL1 and ADAM17 in the pathogenesis of diffuse parenchymal lung diseases (DPLDs) in the human population. The concentration of CX3CL1 and ADAM17 was measured by the enzyme-linked immunosorbent assay (ELISA) test in bronchoalveolar lavage fluids of patients suffering from different DPLDs. The concentration of CX3CL1 was significantly higher in patients suffering from idiopathic pulmonary fibrosis (IPF) and hypersensitivity pneumonitis patients compared to the control group. A significantly higher concentration of CX3CL1 was measured in fibrotic DPLDs compared to non-fibrotic DLPD patients. We found a positive correlation of CX3CL1 levels with the number of CD8+ T cells, and a negative correlation with CD4+ T cells in BALF and diffusion capacity for carbon monoxide. The concentration of ADAM17 was significantly lower in the IPF group compared to the other DPLD groups. We noticed a significantly higher CX3CL1/ADAM17 ratio in the IPF group compared to the other DPLD groups. We suggest that CX3CL1 has a distinctive role in the pathogenesis of DPLDs. The level of CX3CL1 strongly correlates with the severity of lung parenchyma impairment. The results suggest that high values of CX3CL1/ADAM17 could be diagnostic markers for IPF.

CT Findings in Pulmonary and Abdominal Sarcoidosis. Implications for Diagnosis and Classification

Sarcoidosis is a granulomatous disorder of unknown etiology characterized by noncaseating granulomas virtually in every organ and tissue. This finding represents the most important diagnostic clue to reach a correct definition of sarcoidosis, although the biopsy is invasive and has several risk procedures. Several efforts are made to suspect the diagnosis of sarcoidosis by combining noninvasive elements, in particular from imaging, though these findings are often nonspecific and reflect the wide multifactorial pathogenesis. Every effort should be made to obtain a detailed radiological picture that, if associated with a suggestive clinical picture, could avoid the need of biopsy in some specific cases. In this narrative review, we aim to describe main computed tomography (CT) features of pulmonary and abdominal sarcoidosis, by reporting strengths and limits of this technique, in particular for the identification of extrapulmonary, isolated disease.