Speaker's Highlight

• Don Sin University of British Columbia, St. Paul Hospital (Canada)
  Kenneth R. Chapman Toronto General Hospital Research Institute (Canada)
• Parameswaran Nair McMaster University (Canada)
  Carolyn Calfee UCSF (U.S.A.)
• Gregory P. Downey University of Colorado School of Medicine (U.S.A.)
  David A. Schwartz University of Colorado School of Medicine (U.S.A.)
• Neil Schluger Tuberculosis Control Branch, California Department of Public Health (U.S.A.)
  Nick Kim Critical Care & Sleep Medicine, University of California San Diego (U.S.A.)
• Nicola Hananiah Baylor College of Medicine (U.S.A.)
  Jae-Joon Yim Seoul National University College of Medicine (Republic of Korea)
• Koichiro Asano Tokai University School of Medicine (Japan)
  Diahn-Warng Perng Taipei Veterans General Hospital (Taiwan)
• Konstantinos Kostikas University of Ioannina (Greece)
  Karin Klooster University Medical Center Groningen (Kingdom of the Netherlands)

• Radiographic Patterns of Drug-Induced Interstitial Lung Disease

  Drug-induced interstitial lung disease (ILD) is an important cause of new or worsening breathlessness, cough and reduced exercise tolerance. Its imaging appearance can resemble infection, pulmonary oedema, connective tissue disease or progression of an underlying cancer, so radiographs must be interpreted alongside the medication history and clinical timeline.

  The range of causative medicines is broad. Common examples include amiodarone, nitrofurantoin, methotrexate, chemotherapy, immune checkpoint inhibitors, targeted therapies and some biological agents. Toxicity may develop soon after treatment begins, after months or years of exposure, or following a dose increase.

  In Australia, the issue crosses several clinical settings: a patient receiving immunotherapy in Melbourne, an older adult taking long-term nitrofurantoin in Perth, or someone prescribed amiodarone through a regional cardiology service may present to different parts of the healthcare system. Recognising characteristic radiographic patterns helps clinicians arrange timely review, exclude infection and discuss treatment changes safely.

  Why The Medication Timeline Matters

  Drug-induced lung injury is a diagnosis of probability rather than a finding established by imaging alone. The radiologist or respiratory physician should record the medicine, dose, start date, recent changes, cumulative exposure and any previous episodes of toxicity. A symptom-free interval does not exclude medication injury, particularly with agents associated with cumulative damage.

  The Australian medicines market adds practical complexity. A medicine may be supplied through the Pharmaceutical Benefits Scheme, a hospital formulary or private care, while complementary products and medicines obtained overseas may not appear in the primary medication list. The Therapeutic Goods Administration regulates medicines under Australia’s therapeutic goods framework, but clinicians still need to verify what the patient is actually taking.

  The Role Of Chest Radiography

  A chest X-ray is often the first investigation because it is accessible in emergency departments, general practices and regional hospitals. It may show bilateral reticular or reticulonodular opacities, patchy air-space consolidation, lower-zone volume loss or diffuse alveolar shadowing. A normal radiograph, however, does not reliably exclude early drug-related ILD.

  Plain films are useful for assessing progression and identifying complications such as pleural effusion or pneumothorax. They are less reliable for defining the interstitial pattern. When symptoms persist, oxygenation worsens or the film is abnormal without a clear explanation, high-resolution computed tomography (HRCT) is usually the more informative examination.

  Ground-Glass And Nonspecific Interstitial Patterns

  Ground-glass opacity is one of the most frequent HRCT findings. It reflects partial displacement of air by inflammation, fluid, cells or mild fibrosis and is therefore highly nonspecific. Drug toxicity may produce bilateral, symmetrical ground-glass change, often with fine reticulation and lower-lobe predominance.

  A nonspecific interstitial pneumonia pattern consists of ground-glass opacity, fine reticulation, traction bronchiectasis and relative preservation of the immediate subpleural lung. It is reported with medicines such as methotrexate, some chemotherapy agents and selected immunotherapies. The pattern should prompt comparison with previous scans and assessment for connective tissue disease, especially when symptoms are gradual.

  Organising Pneumonia And Hypersensitivity Patterns

  Organising pneumonia commonly appears as patchy consolidation in the peripheral or peribronchovascular lung, frequently in the lower zones. Opacities can migrate, fluctuate or form perilobular bands. Air bronchograms are common, while pleural effusions are less prominent than in pulmonary oedema. Drug-related organising pneumonia has been associated with immune checkpoint inhibitors, amiodarone and several anti-cancer treatments.

  A hypersensitivity pneumonitis-like pattern may include centrilobular ground-glass nodules, mosaic attenuation, air trapping and patchy perfusion differences. Expiratory HRCT is particularly valuable because air trapping may be missed on standard images. Exposure history remains essential: mould, birds, workplace dust and medications can produce overlapping appearances. In regional Queensland or New South Wales, work and home exposures may coexist, making a detailed occupational history worthwhile.

  Severe Presentations And High-Risk Patterns

  Diffuse alveolar damage is the radiographic and pathological pattern associated with severe acute lung injury. HRCT may show widespread ground-glass opacity, dependent consolidation, septal thickening and a “crazy-paving” appearance. Patients are often markedly hypoxaemic, and the differential diagnosis includes viral or Pneumocystis infection, acute respiratory distress syndrome and cardiogenic oedema.

  Amiodarone toxicity can produce ground-glass opacity, consolidation and interstitial fibrosis, sometimes with high-attenuation areas in the liver or lung due to iodine-rich drug deposition. Bleomycin and other cytotoxic agents may cause an acute pneumonitis or later fibrotic change. When a patient receiving cancer therapy in Sydney or Brisbane develops rapidly progressive infiltrates, urgent multidisciplinary assessment is needed rather than assuming the appearance represents tumour progression.

  Fibrosis, Nodules And Ancillary Clues

  Established drug-related fibrosis may resemble usual interstitial pneumonia, with basal and subpleural reticulation, architectural distortion, traction bronchiectasis and honeycombing. A new fibrotic pattern after medication exposure should be compared with any pre-treatment CT. Pre-existing idiopathic pulmonary fibrosis can also deteriorate during treatment, creating a difficult distinction between disease progression, acute exacerbation and drug toxicity.

  Some agents produce less typical findings. Pulmonary nodules, pleural disease, lymphadenopathy, pulmonary haemorrhage or eosinophilic infiltrates may occur depending on the medicine and immune response. A high-attenuation thyroid or liver, peripheral consolidation or a distribution that changes over time can provide useful supporting clues, but none is diagnostic in isolation.

  Integrating Imaging With Clinical Evidence

  The assessment should include infection testing, cardiac evaluation, renal and hepatic function, autoimmune screening when indicated, and pulmonary function tests after the patient is stable. Bronchoscopy with bronchoalveolar lavage may help exclude infection or malignancy, although lavage findings are generally supportive rather than specific. A multidisciplinary discussion between radiology, respiratory medicine, pharmacy, oncology and the prescribing team is often the safest approach.

  Immunotherapy-associated pneumonitis deserves particular care because symptoms can be mild initially and may worsen quickly. Imaging severity, oxygen requirement and clinical trajectory guide decisions about withholding treatment and using corticosteroids. Local protocols vary, and medication cessation or rechallenge should be managed by the relevant specialist team rather than based on an isolated scan.

  Reporting And Follow-Up In Practice

  A useful report describes the dominant pattern, distribution, severity, comparison with prior imaging and the leading alternatives. Instead of simply stating “interstitial changes,” it is more helpful to write that the scan demonstrates bilateral lower-lobe ground-glass opacity with fine reticulation, without honeycombing, compatible with a cellular NSIP or drug-related pneumonitis pattern in the appropriate clinical context.

  Follow-up imaging should answer a specific question: has the abnormality improved after withdrawal, progressed despite treatment, or evolved into fibrosis? In Australia, long travel distances from rural communities to tertiary respiratory services can delay review, so clear communication with the referring doctor is important. A radiology reference such as this clinical imaging resource can support broader learning, but patient management must remain individualised.

  The most practical safeguard is a medication reconciliation whenever new bilateral lung opacities appear. Match the scan pattern to the exposure timeline, compare with earlier imaging, exclude infection and cardiac causes, and involve the prescribing specialist early. That disciplined sequence turns a nonspecific radiographic abnormality into a safer, clinically useful assessment.

  Richard Russell Nuffield Department of Clinical Medicine, University of Oxford (United Kingdom)
• Mona Bafadhel King’s College London (United Kingdom)
  David Jackson Guy’s and St Thomas’ Hospital, King’s College London (United Kingdom)
• James Chalmers University of Dundee (United Kingdom)
  David Price University of Aberdeen (United Kingdom)