CTICasesPulmonary Alveolar Proteinosis — Geographic Crazy Paving
Imaging findings
CT demonstrates a striking geographic crazy paving pattern: areas of ground-glass opacity with overlying septal thickening and intralobular reticulation are sharply demarcated from completely uninvolved lung parenchyma at lobular boundaries. The pattern is predominantly bilateral but geographically distributed, with secondary pulmonary lobules either completely involved or completely spared. This is one of the most photogenic examples of the crazy paving pattern seen in this teaching series. Diagnosis was confirmed by anti-GM-CSF antibodies in BAL fluid, with whole lung lavage planned.
Key takeaways
Pulmonary alveolar proteinosis (PAP) produces the classic crazy paving pattern on CT: ground-glass opacity with superimposed intralobular septal thickening distributed in a geographic pattern with sharp lobular boundaries. The geographic distribution with complete lobular sparing and complete lobular involvement in adjacent areas is characteristic. Anti-GM-CSF autoantibodies are highly sensitive and specific for autoimmune (primary) PAP and can confirm the diagnosis without invasive lavage in appropriate clinical context. The pathophysiology involves anti-GM-CSF antibodies blocking macrophage activation and surfactant clearance.
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