대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Pulmonary alveolar proteinosis

Radiologic Findings

Initial chest CT image shows an approximately 2 cm sized subsolid nodule (arrow) with a peripheral halo in the left lower lobe. Initial impression was focal bacterial pneumonia or eosinophilic pneumonia. The patient did not complain of any signs of infection.
Follow up CT images performed 10 days later showed consolidation with peripheral GGO and interlobular septal thickening, demonstrating a crazy-paving pattern appearance, the extent of which was increased compared with the initial CT scan.
A video-associated thoracoscopic (VATS) biopsy was performed to obtain a diagnosis, and the patient was subsequently diagnosed with PAP.

Brief Review

PAP is a relatively rare disease that is classified into idiopathic and secondary forms based on the presence of hematologic malignancy, compromised immunity, or exposure to materials such as silica and cement. PAP consists of intra-alveolar accumulation of lipoproteinaceous material resulting from a defective turnover of surfactant. In addition, there is typically a uniform accumulation of PAS-positive material in all alveolar spaces. Electron microscopy shows that the intraalveolar material consists of amorphous, granular debris containing numerous osmiophilic, fused membrane structures with a periodicity of 4.7 nm and resembling lamellar bodies and tubular myelin.
Although typical CT features of PAP are GGO with interlobular septal thickening (crazy-paving appearance), distributed diffusely or geographically involving the bilateral lung parenchyma, various CT image findings are possible ranging from GGO to dense consolidation.
The majority of the literature investigating CT finding of PAP have reported the diffusely and bilaterally distributed crazy-paving appearance, and little reports of unilateral or asymmetric patterns of PAP were suggested. In the case presented here, nodular and localized pattern of PAP is rare and interesting manifestations. In conclusion, it is important for radiologists to be aware of potential atypical imaging findings of PAP in order to provide a correct diagnosis. Along these lines, PAP can present as a solitary nodular lesion or unilateral focal lesion.

References

1. Frazier AA, Franks TJ, Cooke EO, Mohammed TL, Pugatch RD, Galvin JR. From the archives of the AFIP: pulmonary alveolar proteinosis. Radiographics 2008;28:883-99; quiz 915.
2. David MH, Alexander AB, Heber M, Theresa CM, Nestor LM, Jacques R. Fleischner Society: glossary of terms for thoracic imaging. Radiology 2008; 246:697−722

Keywords

Lung, Metabolic and storage lung disesae,