Objective: Pulmonary mucormycosis is an aggressive opportunistic fungal infection. We set out to evaluate the CT and MRI features of pulmonary mucormycosis.
Materials and methods: Through a search of the electronic medical record from 2007 to 2017, we identified 30 patients with definite or probable mucormycosis. Two radiologists reviewed the initial chest CT examinations for the presence of features including the "reverse halo" sign, large ground-glass halo, and peripheral lesion distribution. Additional CT and MRI studies were reviewed to evaluate evolution over time.
Results: The majority (67%) of patients had lesions with the reverse halo sign at some point in the disease course. A ground-glass halo larger than the lesion was seen in 53% of patients. Notably, lesions had a peripheral predominance in 87% of cases. Through careful review of images, a perivascular ground-glass precursor lesion was identified in 20% of patients 1-2 weeks before a consolidation developed. In five (17%) patients, CT showed a multifocal pneumonia appearance. Finally, MRI of two patients showed T2-hypointense rims and central nonenhancement, a finding we refer to as the "black hole" sign.
Conclusion: Large nodules or consolidations with an associated reverse halo sign or large perilesional ground-glass halos are common in mucormycosis. Lesions tend to show a peripheral predominance, and a perivascular ground-glass focus preceded nodular lesions in some cases. In some patients with severe disease, imaging features evolved to show a multifocal pneumonia pattern, and this pattern was associated with a high mortality rate.
Keywords: Zygomycetes; angioinvasive fungal infection; mucormycosis; reverse halo sign.