Black pleura sign (lungs)

The black pleura sign is a feature described in pulmonary alveolar microlithiasis. It is seen as a strip of tangential peripheral lucency underlying the ribs as compared to the adjacent diffusely dense calcified lung.

Although termed black pleura, it actually represents subpleural sparing of pulmonary calcification that occurs in the alveoli centrally within the secondary pulmonary lobules. It was initially described on plain radiographs as a means of identifying alveolar microlithiasis, but is also demonstrated on chest CT.

See also