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Objective:
Connective tissue diseases (CTD) are conditions of autoimmune etiology that predominantly affect skin, muscles, and joints, and often present with lung fibrosis. Diagnoses include myositis, scleroderma, rheumatoid arthritis, and antisynthetase syndromes, all of which are characterized by inflammation, tissue damage, and abnormal repair. Histological analysis of lung tissue from CTD patients typically reveals either a cellular, fibrotic, or mixed pattern of nonspecific interstitial pneumonia (NSIP). NSIP is lower lobe predominant with homogeneous ground glass opacities (GGO) and associated traction bronchiectasis and lobar volume loss. The radiographic presence of subpleural sparing strongly supports the diagnosis of NSIP, but its absence does not exclude it. This is an ongoing study with a purpose of better understanding the imaging findings of NSIP within the context of CTDs. These correlates can then be used to assess disease progression with CT only. An improved understanding of evolution of the disease to identify disease earlier and more accurately would better inform treatments.

Materials and Methods:
There were 400 patients with NSIP pattern on chest CT were identified using M*Modal, of whom those with a charted CTD diagnosis were selected. Cardiothoracic radiologists then excluded those with mischaracterized NSIP, and we report characteristics of 31 of those participants in this ongoing study. Images were reviewed to determine the extent of disease, presence of peripheral sparing, cellular or fibrotic nature of the NSIP, angle of the RLL bronchus, degree of lobar involvement, homogeneity, honeycombing, and esophageal involvement. The radiologists graded the severity of disease by consensus using an adapted version of a previously published grading system.

Results:
This interim analysis included imaging from 31 unique patients. Of these 31 patients, five patients had early disease (ED) (16%) with an organizing pneumonia (OP) and cellular NSIP pattern, 24 had mid-disease (MD) (77%) with a mixed NSIP pattern, and two patients had late disease (LD) (7%) with a fibrotic NSIP pattern. The average age in ED was 57.4 years, MD, 64.5 years, and LD, 76 years. One out of five (20%) showed peripheral sparing in ED, 12 out of 24 (50%) showed peripheral sparing in MD, and one out of two (50%) showed peripheral sparing in LD. Honeycombing was present only in MD (<em>n</em> = 2) and LD (<em>n</em> = 1). The average RLL bronchus angle was 6 degrees deviation in ED, 25 degrees in MD, and 30 degrees in LD. As per the noted grading system, ED had an average grade of 6/16, MD an average grade of 8/16, and LD an average grade of 11/16.

Conclusion:
Our preliminary results show that ED is associated with fewer architectural disruptions when compared to MD and LD. Honeycombing was not seen in ED. The RLL bronchus angle showed increasing deviation with progression of disease. However, no disease stage showed cyst formation. These findings indicate that architectural distortion is prominent in late disease and suggests that targeting fibrosis early in the disease process could improve outcomes.