CT morphological features of the reversed halo sign in pulmonary paracoccidioidomycosis.

OBJECTIVE

The purpose of this study was to identify morphological characteristics of the reversed halo sign (RHS) on chest CT in patients with pulmonary paracoccidioidomycosis (PCM) that may aid the diagnosis of this fungal disease.

METHODS

We retrospectively reviewed chest CT images from 23 patients with proven pulmonary PCM who demonstrated the RHS. Two chest radiologists analysed the morphological characteristics of the lesions and reached decisions by consensus.

RESULTS

We identified 64 RHSs on CT images from the 23 patients. Multiple lesions were observed in all cases, with middle and lower lung zone predominance occurring in 17 patients (73.9% of cases). 34 (53.1%) RHSs were round and 30 (46.9%) were oval. Outer borders of the RHSs were smooth in 32 (50%) lesions, nodular in 16 (25%) lesions and irregular/spiculated in 16 (25%) lesions. Ground-glass opacity was observed inside 63 (98.4%) lesions.

CONCLUSION

Our data suggest that morphological characteristics of the RHS on chest CT, such as the presence of multiple lesions, middle and lower lung zone predominance and a spiculated RHS ring, as well as the association with other parenchymal patterns, should lead radiologists to include PCM in the differential diagnosis of PCM in endemic areas.

ADVANCES IN KNOWLEDGE

This is the largest series of patients with RHS due to PCM and is also the first study to report RHS lesions with spiculated or irregular walls. The study adds information regarding morphological characteristics of the RHS that may raise suspicion of PCM on chest CT, particularly in endemic areas of the disease.