Alveolar proteinosis with hypersensitivity pneumonitis: a new clinical phenotype.

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.