Correct!
3. Pulmonary alveolar proteinosis
The resolution of the medial right apical nodule and the decrease in mediastinal lymphadenopathy suggests a positive response to antifungal therapy, not worsening of infection. Increased pressure edema can certainly manifest as worsening smooth interlobular septal thickening, but often such pulmonary parenchymal findings are associated with other features of increased pressure edema, such as cardiac enlargement, small pleural effusion, fat infiltration, and other findings of third-spacing, but these latter findings are lacking in this case. COVID-19 infection can rarely present with ground-glass opacity and interlobular septal thickening, but this pattern is uncommon and typically associated with significant respiratory symptoms as well as physiologic abnormalities, and this CT pattern occurs in the acute phase of the infection, not typically months later. Pulmonary parenchymal lymphoma is rare in general, and, as noted previously, often presents as multiple non-solid or part-solid nodules or direct extension of peribronchial or mediastinal lymph node involvement. However, intrathoracic lymphoproliferative disorders may manifest in numerous different ways, including interlobular septal thickening, given the presence of lymph tissue within the interlobular septae. Nevertheless, this presentation of intrathoracic lymphoproliferative disorder is very rare, and the patient’s underlying diagnosis of MDS-MLD is more associated with development of acute myeloid leukemia rather than lymphoma. Medication-induced pulmonary injury, or drug reactions, may be classified using the American Thoracic Society idiopathic interstitial pneumonia classification system- many drug reactions present with these patterns. Other patterns of parenchymal injury related to medication include lymphadenopathy and sarcoid-like reactions, pleural effusion, nodules, and an acute eosinophilic pneumonia-like pattern. The latter may somewhat resemble this patient’s CT scan, but this reaction pattern is quite rare and, based on the CT performed 7 months earlier, appears to be developing over time rather than acutely. The pattern at CT is consistent with the “crazy-paving” pattern which is suggestive of pulmonary alveolar proteinosis.
Which of the following represents the most appropriate next step for the patient’s management? (Click on the correct answer to be directed to the twelthof fourteen pages).