A 30-year-old immunocompromised patient presents with fever and dyspnea. Chest CT shows a nodule surrounded by a halo of ground-glass opacity ('halo sign'). Which of the following is the most likely causative organism?

• A Mycobacterium tuberculosis
• B Pneumocystis jirovecii
• C Streptococcus pneumoniae
• D Aspergillus fumigatus ✓

Explanation

The halo sign (nodule surrounded by ground-glass opacity representing hemorrhage) is the classic CT finding of invasive pulmonary aspergillosis in immunocompromised patients, particularly those with neutropenia. Tuberculosis typically shows cavitary upper lobe lesions. Streptococcus pneumoniae causes lobar consolidation. Pneumocystis jirovecii causes diffuse bilateral ground-glass opacities, not a halo sign.

Reference: Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, 9th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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