Serial chest CT findings in interstitial lung disease associated with polymyositis-dermatomyositis

A retrospective study was carried out in two institutions to determine serial changes in the pattern, distribution, and extent of interstitial lung disease (ILD) associated with polymyositis (PM)-dermatomyositis (DM) using HRCT.

Twenty patients with PM-DM and clinical suspicion of ILD who underwent at least two serial HRCT examinations were retrospectively evaluated by two readers. Patients were classified according to the dominant CT pattern which was correlated with clinical evolution and underlying histology when available (n=6).

Patients were classified into four groups according to the dominant pattern: ground-glass attenuation and reticulation (group 1, n=9); honeycombing (group 2, n=4); airspace consolidation (group 3, n=4), and normal or almost normal lung (group 4, n=3). Under medical treatment, serial HRCT showed that the extent of areas of ground-glass opacities (group 1) decreased in five patients, stabilized in two, and increased in two. Pathologic findings demonstrated usual interstitial pneumonia (UIP) in two cases and unspecified interstitial pneumonia in one. In group 2, extent of honeycombing increased in three cases and stabilized in one. In group 3, dramatic resolution of airspace consolidation occurred in three cases. Clinical deterioration with extensive consolidation at CT and diffuse alveolar damage (DAD) at histology occurred in one patient of each of the three previous groups. Lesions stayed invisible or progressed slightly in the fourth group.

In ILD associated with PM-DM, clinical deterioration and DAD in the follow-up can be observed whatever the HRCT pattern. However, unfavorable evolution is constant when honeycombing is present at the initial CT.