Differential diagnosis of the reversed halo sign (RHS). AIA, angioinvasive aspergillosis; AIS, adenocarcinoma in situ; COP, cryptogenic organising pneumonia; LPA, lepidic predominant adenocarcinoma; N, no; NSIP, non-specific interstitial pneumonia; OP, organising pneumonia; PJP, Pneumocystis jiroveci pneumonia; PZ, pulmonary zygomycosis; RFA, radiofrequency ablation; Y, yes. *Includes immunosuppression, close contact with a person with tuberculosis, residence in or immigration from country where tuberculosis is common, residence in nursing home or prison, homelessness. **Includes cavitary lesions, lobular consolidation, centrilobular nodules and tree-in-bud opacities, as well as nodularity of the wall of the RHS and small nodules inside the RHS. ***Suspected in patients with acquired immunedeficiency syndrome. +Upper respiratory tract disease and non-specific glomerulonephritis, and elevation of cytoplasmic antineutrophil cytoplasmic antibody titres. ++Nodularity of the wall of the RHS and small nodules inside the RHS, possibly associated with symmetrical bilateral hilar and right paratracheal lymphadenopathy and small nodules with perilymphatic distribution. †Associated with connective tissue diseases, aspiration, drug toxicity, hypersensitivity pneumonitis, infection or radiation therapy. ††Less likely. #Diagnosis #Pulmonary #Radiology #RHS #ReverseHaloSign #Differential #Algorithm
