A case of progressive pulmonary alveolar proteinosis with lymphadenopathy revealed on 18 F-FDG PET/CT

Pulmonary alveolar proteinosis (PAP) is a rare lung disease, which may cause repeating infections. A 36-year-old man had repetitive admissions to our hospital, beginning two years ago, due to episodes of severe dyspnea. Serial computed tomography (CT) scans revealed extensive ground-glass opacities with interlobular/intralobular septal thickening, diffuse consolidations in both lungs and enlarged lower paratracheal lymph nodes. The first biopsy of the right lung and of a mediastinal lymph node showed no evidence of malignancy. Fluorine-18-fluorodeoxyglucose positron emission tomography/CT (18 F-FDG PET/CT) was performed in June 2020 following a case of clinical and radiological deterioration to exclude the possibility of malignancy. Positron emission tomography/CT showed increased 18F-FDG uptake in the both lungs and in enlarged mediastinal lymph nodes, with maximum standardized uptake value (SUVmax) of 13.5 and 9.2 respectively. Computed tomography-guided biopsy of the right lower lobe supported the diagnosis of pulmonary alveolar proteinosis.