Reverse halo sign of cryptogenic organizing pneumonia


Cryptogenic organizing pneumonia (COP), either primary or secondary is considerably more likely than invasive fungal infection, due to the very short duration of neutropenia prior to radiologic abnormality, prior autograft rather than allograft (thus not graft versus host disease) and seeming lack of respiratory symptoms. The reverse halo sign (also known as the atoll sign) is typical of cryptogenic organizing pneumonia and seen more frequently than in invasive fungal infection. When seen in invasive fungal infection the reversed halo sign is said to be more suggestive of zygomycetes rather than invasive aspergillosis.