A 75-year-old woman presented with dyspnea and acute respiratory failure (oxygen saturation 89%). A computed tomography (CT) scan was performed (Fig. 1A–C), and the differential diagnosis included tuberculosis reactivation and atypical pneumonia. The patient was initiated on empiric treatment with meropenem and systemic corticosteroids. The interferon-gamma release assay for Mycobacterium tuberculosis was positive, and the acid-fast bacilli (AFB) smear microscopy was negative. Despite the addition of linezolid and weight-adjusted antituberculosis therapy, the patient's condition continued to deteriorate, necessitating the postponement of a planned bronchoscopy with bronchoalveolar lavage. The patient ultimately succumbed 15 days after admission. A postmortem CT-guided biopsy revealed acute fibrinous and organizing pneumonia (AFOP) (Fig. 1D–F). The microbiological results demonstrated a positive polymerase chain reaction (PCR) for the M. tuberculosis complex.

Fig. 1.

Chest computed tomography at admission (A) and a few days later (B) with coronal reconstruction with maximum intensity projection (C), demonstrating volume loss of the right upper lobe and atelectasis, patchy centrilobular nodules of irregular morphology and peribronchovascular distribution (more evident in C). Detail of “fibrin ball” occupying alveolar space (hematoxylin and eosin, ×10) (D). CD68+ staining in epithelioid histiocytes (E). Masson's trichrome staining shows fibrin clusters (F).

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AFOP is a rare interstitial pneumonia characterized by the presence of fibrin “balls” within alveolar spaces, with a mortality rate of 50%. In contrast to diffuse alveolar damage, AFOP is characterized by the absence of hyaline membranes and a more irregular and less extensive distribution of fibrin. The clinical presentation is non-specific, typically acute or subacute, and the known causes include drugs, hypersensitivity pneumonitis, collagen disease, infections, and idiopathic cases.1,2M. tuberculosis is a rare cause of this condition.2,3 This case shares key aspects with that of Zhao X et al.,3 including rapid deterioration with progression of pulmonary lesions and the need for biopsy for definitive diagnosis. It emphasizes the importance of postmortem examinations, including histopathologic and microbiologic analyses, in clarifying ambiguous clinical conditions.