The role of PET-CT in decision making on the treatment of localized nodular form of pulmonary AL-amyloidosis

Summary

Depending on the extent of organism affected, there is a systemic (amyloid is deposited in the interstitial space of multiple tissues and organs) and localized (amyloid is deposited in one or a few solitary lesions) form of amyloidosis. Localized forms of amyloidosis have a significantly better prognosis than the systemic ones. The respiratory tract might be affected by diffuse interstitial involvement, associated with systemic AL-amyloidosis, as well as localised involvement of respiratory tract (localised laryngotracheobronchial amyloidosis) or pulmonary parenchyma called nodular form of localized pulmonary amyloidosis. Tracheobronchial form may affect larynx and bronchial tree, and forms plaques or nodules in the epithelium of the respiratory tract. Nodular form causes spherical or irregular lesions in the pulmonary parenchyma, indistinguishable from pulmonary parenchyma metastases. We describe a two-year follow up of a patient with nodular form of pulmonary amyloidosis. The patient had multiple lesions in both lungs, clearly visible on HRCT (High Resolution Computer Tomography) that intensively accumulated fluorodeoxyglucose (FDG) during the first PET-CT. At the time of diagnosis, the largest lesion SUV for FDG accumulation was 8.2. Histochemical analysis showed that amyloid consisted of the light λ chains, i.e. AL-amyloid. Investigations to detect a systemic form of amyloidosis, if present, were negative. The patient had no monoclonal immunoglobulin either in the urine or serum (negative immunofixation) and had normal levels of free light chains in the serum. Her symptoms were previously suggestive of the Sjögren’s syndrome. However, the rheumatologist consulted at the time of diagnosis of the nodular form of pulmonary amyloidosis did not find any signs of an active systemic connective tissue disorder. CRP was repeatedly normal. When systemic AL-amyloidosis was excluded, we decided to only monitor lesion development with no treatment intervention. The patient had 3 PET-CTs. CT showed that no lesions enlarged, some lesions decreased in size slightly. It should be emphasized that follow-up PET-CTs did not show increased FDG accumulation. We assume that the increased FDG accumulation in pulmonary lesions seen during the first PET-CT was due to the activity of the cells that formed this amyloid and that this activity spontaneously ceased, leading to normalization of FDG accumulation in pulmonary nodules. PET-CT is useful for monitoring of the development of pulmonary nodular amyloidosis. Normalization of originally increased FDG accumulation in amyloid lesions suggests cessation of the process of amyloid formation and is a positive prognostic sign.

Key words:
localized amyloidosis – nodular pulmonary amyloidosis – tracheobronchial amyloidosis – AL-amyloidosis – PET-CT imagination – multiple myeloma