Presentation
Increasing shortness of breath and cough for 2 months. History of rheumatoid arthritis treated with methotrexate.
Patient Data
Lower zonal predominant diffuse reticular opacities with volume loss and pleural thickening. No consolidation or pleural effusion. Findings suspicious for fibrosing ILD. HRCT recommended.
Diffuse bilateral mosaic attenuation with lower zonal predominant gas trapping on expiratory images. 'Triple density' appearance within the lung bases. Subpleural and peribronchovascular irregular interlobular septal thickening, traction bronchiolectasis and parenchymal distortion, with no gradient or honeycombing. No pulmonary nodules or pleural effusion. Mediastinal and hilar adenopathy.
Findings are most in keeping with fibrotic hypersensitivity pneumonitis. Differentials of atypical infection or rheumatoid pulmonary fibrosis.
Case Discussion
The case demonstrates a typical fibrotic hypersensitivity pneumonitis secondary to methotrexate-induced pulmonary drug toxicity. Infection and hypersensitivity pneumonitis secondary to other environmental triggers were excluded clinically and on antigen testing. Symptoms improved with steroids and cessation of methotrexate.
Pulmonary drug toxicity from methotrexate is not uncommon. The exact aetiology is uncertain but hypothesised to result from pneumonitis secondary to direct alveolar drug toxicity, hypersensitivity pneumonitis, and superimposed atypical infection from immune suppression. The imaging features of methotrexate pulmonary drug toxicity are variable and can include ground-glass opacities, organising pneumonia and pleural effusions, in addition to hypersensitivity pneumonitis.
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