The "reversed halo" sign in pneumonococcal pneumonia: a review with a case report.

The "reversed halo" sign (RHS) is a distinct radiological sign representing a focal rounded area of ground-glass opacity surrounded by a more or less complete ring of consolidation. Initially, it was reported in two cases of cryptogenic organizing pneumonia and was considered to be relatively specific of the disease. Since then, it has been reported in a wide variety of clinical entities, thus reducing its specificity. We describe the reversed halo sign in a case of pneumonococcal pneumonia. To the best of our knowledge, this is the first report in English literature. The presence of the "reversed halo" sign during the resolution phase of pneumonococcal pneumonia has serious implications. First, it further reduces its specificity. Second, it opens new areas of research regarding its significance in cases of cryptogenic organizing pneumonia.