Pulmonary amyloidosis mimicking interstitial lung disease and malignancy - A case series with a review of a pulmonary patterns

BACKGROUND: Amyloidosis is an uncommon condition, which results from accumulation of misfolded extracellular insoluble protein in tissues and organs of the body, causing its damage and dysfunction. Histologically, after staining with Congo red, the amyloid deposits show an apple-green birefringence under polarized light microscope. Amyloidosis can affect all organ systems and is classified into hereditary or acquired, localized or systemic. Respiratory involvement occurs in 50% of the patients with amyloidosis and it may take tracheobronchial, nodular parenchymal, diffuse alveolar septal and lymphatic forms. METHODS: We report four cases of pulmonary amyloidosis. A female patient with localized form of tracheobronchial and nodular parenchymal pulmonary amyloidosis, which was initially misdiagnosed as sarcoidosis. A male patient who was referred to our department for further evaluation of multiple tumors in lungs accompanied by mediastinal lymphadenopathy, liver and peritoneal tumors. A male patient with suspect of lung malignancy. A male patient with diagnosed idiopathic pulmonary fibrosis and the possibility of malignancy. RESULTS: All the diagnoses were established by demonstration of amyloid protein in tissue specimens obtained in transbronchial or open lung biopsies. CONCLUSIONS: Due to its nonspecific clinical and radiological findings, amyloidosis can often mimic other diseases and should be considered as one of the differential diagnoses. In order to confirm the diagnosis, proving the presence of amyloid deposition with positive Congo red staining in respiratory specimen is mandatory.