Correct!
4. Erdheim-Chester disease
While the multifocal nature of the abnormalities does raise concern for malignancy, distal osseous sclerotic lesions would be unusual for untreated bronchogenic malignancy, particularly small cell carcinoma. Furthermore, the perivascular infiltration is a pattern that would be unusual for bronchogenic malignancies, even small cell carcinoma- this malignancy often presents with a perihilar or hilar mass rather than diffuse perivascular soft tissue infiltration. Amyloidosis may cause deposits of material in unusual locations, although perivascular soft tissue infiltration is not typical; focal soft tissue masses would be expected. Pulmonary parenchymal involvement in amyloid may manifest with interstitial infiltration, but the pattern seen- often referred to as “alveolar-septal” amyloid- characteristically manifests as interlobular septal thickening usually peribronchovascular and subpleural nodules, and nodules along the interlobular septae, possibly with associated fibrotic changes, rather than the smooth interlobular septal thickening seen in this patient. Amyloidosis may also be associated with cystic lung disease, bronchiectasis and single or multiple pulmonary nodules or masses, with or without calcification; tracheobronchial thickening may be seen alone or in combination with pulmonary parenchymal abnormalities in patients with amyloidosis. Non-Hodgkin’s lymphoma (NHL) is always a consideration when infiltrative mediastinal soft tissue is present, and NHL can present with perivascular soft tissue infiltration. Furthermore, NHL may present with interlobular septal thickening. Bone lesions are also possible, including sclerotic foci, in patients with NHL, although this latter manifestation of NHL is not typically symmetric and so distally located. The orbital lesions would also be unusual for NHL, but it is the combination of these various abnormalities in the same patient that make NHL unlikely overall. Fibrosing mediastinitis may present with infiltrative mediastinal soft tissue, but often this tissue causes vascular and airway compression due to its fibrous nature. Compression of the pulmonary veins in patients with fibrosing mediastinitis can result in interlobular septal thickening. However, these effects are not observed in this patient. Finally, fibrosing mediastinitis could not account for the osseous and orbital lesions.
Diagnosis: Erdheim-Chester disease (ECD)
Which of the following is true regarding Erdheim-Chester disease?