Correct!
Answer: 4. Pulmonary alveolar proteinosis
The frontal chest radiograph shows bilateral increased lung attenuation consisting of ground-glass opacity and a background of linear and reticular abnormalities.
Pneumococcal pneumonia is a possibility, but this infection most commonly presents either with an air-space pneumonia pattern [homogeneous lung opacity with air bronchograms extending towards the pleural surface] or with a bronchopneumonia pattern [patchy peribronchial nodular consolidation]. Pneumococcal pneumonia uncommonly presents with a bilateral ground-glass appearance on chest radiography; among pulmonary infections that present in this fashion, the so-called “atypical” pneumonias (viral pneumonias, Mycoplasma and Chlamydia pneumonias) and Pneumocystis jiroveci pneumonia are most commonly implicated. Furthermore, the patient’s subacute presentation is less characteristic of pneumococcal pneumonia.
Lung carcinoma most commonly presents as a focal nodule or mass on chest radiography, with or without pleural disease, lymphadenopathy, and / or osseous abnormalities, rather than as a diffuse lung process. However, lung carcinomas, particularly mucinous adenocarcinomas, may present with diffuse lung opacities, and therefore this diagnosis is not completely excluded.
Idiopathic pulmonary fibrosis presents with bilateral, subpleural linear and reticular abnormalities on chest radiography, but these findings are characteristically lower lobe predominant and associated with architectural distortion; occasionally honeycombing may be evident. In this case, there is no architectural distortion and the findings do not show a basal, subpleural predominance.
Although miliary tuberculosis presents as a bilateral abnormality on thoracic imaging studies, typically a small nodular pattern- not linear and reticular opacities- is the dominant finding.
Although a rare disorder, pulmonary alveolar proteinosis is the best choice among the answers provided- this disorder often clinically presents in a subacute fashion, and bilateral areas of ground-glass opacity and sometimes consolidation, superimposed on a background of linear and reticular abnormalities, is a common radiographic presentation for this disorder.
Clinical Course: The patient subsequently underwent thoracic CT (Figures 2) for further characterization.
Figure 2. Representative CT image through mid-lungs (Panel A) and lower lungs (Panel C). Thoracic CT shows bilateral areas of hazy, increased attenuation, representing ground-glass opacity, associated with smooth interlobular septal thickening. Note that abnormal lung areas are geographically distributed and show a sharp demarcation from normal-appearing areas. (Click here for a movie of the CT scan)
Regarding the CT appearance of the pulmonary process, which of the following is most accurate?
