Aqeel A. Chowdhry, MD

Tan-Lucien H. Mohammed, MD, FCCP

Frontal radiograph shows nonspecific interstitial pneumonitis from polymyositis. Note the diffuse peripheral interstitial thickening image.

Axial HRCT shows subpleural ground-glass opacities and reticular opacities image. Traction bronchiectasis is out of proportion to reticular opacities. Note the NSIP pattern in polymyositis-dermatomyositis.


Abbreviations and Synonyms

  • Polymyositis-dermatomyositis (PM-DM), dermatomyositis-polymyositis (DM-PM), dermato-polymyositis (DPM)

  • Nonspecific interstitial pneumonia (NSIP), cryptogenic organizing pneumonia (COP), usual interstitial pneumonia (UIP), diffuse alveolar damage (DAD)


  • Polymyositis: Autoimmune inflammatory myopathy (limb girdle & anterior neck muscles)

  • Dermatomyositis: Polymyositis + skin rash


General Features

  • Best diagnostic clue

    • Lung disease in patient with muscle weakness

      • Hint: Elevated diaphragms and subsegmental atelectasis

CT Findings

  • Nonspecific, multiple patterns based on prevailing histology: NSIP, UIP, COP, DAD

    • Aspiration common and may alone result in pulmonary disease or be superimposed on other patterns

    • Hypoventilation also common and may result in atelectasis (discoid or long lines)

  • Distribution similar irrespective of pattern; primarily involves basilar lung

  • NSIP

    • Ground-glass opacities > reticular opacities in bronchovascular distribution

    • Traction bronchiectasis out of proportion to reticular opacities

  • UIP

    • Reticular opacities and honeycombing in subpleural distribution

    • Traction bronchiectasis

  • COP

    • Subpleural focal areas of consolidation

    • Reverse halo sign

  • DAD

    • Acute diffuse ground-glass opacities often with traction bronchiectasis

  • Treatment

    • Ground-glass opacities, consolidation may resolve

  • Extrathoracic manifestations

    • Skin or subcutaneous calcifications in dermatomyositis

    • Dystrophic muscle calcification in polymyositis, uncommon

  • Other

    • High incidence of malignancy, particularly bronchogenic carcinoma

Radiographic Findings

  • 10% have normal chest radiographs

  • Lung volumes reduced

    • Elevated hemidiaphragms due to respiratory muscle weakness, atelectasis

  • Lungs

    • Nonspecific symmetric, basal reticular pattern of parenchymal involvement, may progress to honeycombing (less often)

    • Aspiration

      • Variable appearance, aspiration segments, waxing and waning opacities eventually resulting in fibrosis

  • Soft tissue calcifications

    • Often over bony prominences

    • More common in younger patients

Fluoroscopic Findings

  • Esophagram

    • Upper esophagus predominantly involved may result in reflux or aspiration

    • Swallowing studies useful for diet

    • Obstruction due to stricture or scarring, late

MR Findings

  • Whole body turbo STIR helpful in demonstrating soft tissue inflammatory burden

  • Musculature

    • Signal intensity abnormalities due to inflammation, edema, scarring

    • Symmetric involvement

      • Proximal lower limb girdle, early

      • Progression to proximal upper limb girdle, neck flexors, pharyngeal muscles

      • Facial muscles typically spared

    • Images may be used to guide muscle biopsy

Imaging Recommendations

  • Best imaging tool

    • CT: Affects patient prognosis by demonstrating extent of pulmonary involvement, chronicity of disease process, and response to treatment

    • MR imaging useful to demonstrate areas of muscular involvement


Nonspecific Interstitial Pneumonitis

  • NSIP pattern common in PM-DM

  • No muscle involvement or skin rash

Cryptogenic Organizing Pneumonia

  • COP pattern common in PM-DM

  • No muscle involvement or skin rash

Idiopathic Pulmonary Fibrosis

  • UIP pattern, seen in PM-DM

  • Older age group, no muscle involvement or skin rash


  • NSIP pattern common

  • No muscle involvement or skin rash

  • Esophageal dilatation common, less common in PM-DM

Drug Toxicity

  • Review drug history

  • Commonly chemotherapy drugs (bleomycin, cyclophosphamide, nitrosoureas, etc.)

  • Can result in any pattern seen in PM-DM

Sep 20, 2016 | Posted by in RESPIRATORY IMAGING | Comments Off on Polymyositis-Dermatomyositis

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