title: Localized pulmonary alveolar proteinosis: two case reports.
abstract: BACKGROUND
  Pulmonary alveolar proteinosis (PAP) is a relatively rare disease characterized by abnormal accumulation of surfactant-like material in the alveolar spaces. The classic radiologic findings of PAP include bilateral, symmetric, diffuse ground-glass opacity (GGO) or consolidation. The most common computed tomography (CT) feature of PAP is widespread GGO with thickened interlobular septa, the so-called crazy-paving pattern, which strongly suggests the diagnosis.
  
  
  METHODS
  Here, we report the cases of two young male patients with unusual presentations of PAP. One patient showed localized PAP in the left lower lobe on CT images and the other patient presented with unilateral PAP involving the right lower lung field and recurrence in the same area with the same pattern as the initial manifestation.
  
  
  CONCLUSIONS
  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, and can recur in the same pattern and location.
authors.affiliation: Department of Radiology, Korea University Ansan Hospital, Ansan, Korea.
authors.forename: Seon Jeong
authors.initials: SJ
authors.lastname: Oh
authors.affiliation: Department of Radiology, Korea University Ansan Hospital, Ansan, Korea.
authors.forename: Ji Yung
authors.initials: JY
authors.lastname: Choo
authors.affiliation: Department of Radiology, Korea University Ansan Hospital, Ansan, Korea.
authors.forename: Ki Yeol
authors.initials: KY
authors.lastname: Lee
authors.affiliation: Department of Pulmonology, Korea University Ansan Hospital, Ansan, Korea.
authors.forename: Je-Hyeong
authors.initials: JH
authors.lastname: Kim
authors.affiliation: Department of Radiology, Korea University Ansan Hospital, Ansan, Korea.
authors.forename: Suk Keu
authors.initials: SK
authors.lastname: Yeom
keywords: CT; localized; pulmonary alveolar proteinosis