Computed Tomographic Imaging in Connective Tissue Diseases

Joseph Barnett, FRCR; Anand Devaraj, MD, MRCP, FRCR


Semin Respir Crit Care Med. 2019;40(2):159-172. 

In This Article

Mixed Connective Tissue Disease

Mixed CTD (MCTD) represents a clinical phenotype of more than one CTD, including SSc, PM/DM, and SLE, although the overlapping symptoms may develop sequentially, often over several years. Limited population data are available with regard to its prevalence, one Norwegian study estimated the prevalence at 3.8 per 100,000 adults.[121] This syndrome is strongly associated with autoantibodies to U1 ribonucleoprotein. The majority of cases are associated with pulmonary disease[122] and one-third of patients have ILD.[122] On the basis of studies performed in tertiary centers, PH was considered to be more common in MCTD than in other constituent CTDs.[123] A recent cross-sectional study of unselected patients with MCTD, however, found a frequency of only 3.4%.[124]

NSIP represents the most common HRCT morphology in MCTD ILD,[122] although a PM/DM-type OP is also frequently encountered radiological morphology,[125] with UIP seen in a minority of patients.[122]

A range of other pulmonary abnormalities have been described in MCTD, reflecting the variety of pulmonary abnormalities present in the associated CTDs; pulmonary nodules, bronchiectasis, obstructive small airways disease, pleural thickening, and pleural effusions have all been described.[122,126]

Clinical Significance

The identification of PH is important, as it represents a major cause of mortality in MCTD and therapies toward it are increasingly available. Conversely, few data available on MCTD-ILD suggest that fibrosis may be mild, and progress only mildly over follow-up.[127] Nevertheless, radiological classification of fibrotic morphology has been shown to correlate well with histopathological morphology,[125] and differentiation between NSIP and PM/DM patterns of ILD can be expected to aid treatment algorithms and expectations.