Alveolar proteinosis with hypersensitivity pneumonitis: A new clinical phenotype

ABSTRACT Background and objective: The aim of the present study was to report the features of five patients with concurrent histopathological features of pulmonary alveolar proteinosis (PAP) and hypersensitivity pneumonitis (HP) and their high‐resolution CT (HRCT) appearances. Methods: Patients with histopathological features of both HP and PAP on surgical lung biopsy referred for tertiary review were retrospectively identified. The pathology and HRCT images were semi‐quantitatively scored to evaluate the relative contribution to HP and PAP. Results: Five patients had histopathological features of HP and PAP but had varied HRCT appearances. All had imaging features of PAP to a varying degree with two patients also showing characteristics of HP but three patients had ill‐defined thickened interlobular septa, not typical of either disease. Conclusions: We describe the coexistence of PAP and HP in five patients and discuss possible linkages between these two distinct pathologies. Alveolar proteinosis and hypersensitivity pneumonitis are two distinct diseases. We describe five patients with histopathogical features of both on surgical lung biopsy, their clinical information and the HRCT appearances. Possible associations between the two disorders are also discussed.