A50-55 The Great Mimicker: TB or Not TB?

Abstract Introduction Mycoplasma pneumoniae, the cause of atypical pneumonia, is an elusive pathogen often difficult to diagnose due to its subtle or nonspecific presentation and limited culture media availability. Common symptoms include unproductive cough, wheezing, and malaise; hemoptysis is not typical. Radiographically, M. pneumoniae usually demonstrates centrilobular nodules, bronchial wall thickening, ground-glass attenuation, and patchy consolidation. A miliary pattern on computed tomography (CT) is rare and scarcely reported. We present the first known case of M. pneumoniae infection manifesting with hemoptysis and a miliary pattern on CT, mimicking tuberculosis (TB). Case Presentation 23-year-old with significant secondhand smoke exposure, but no history of smoking or asthma, presented with two weeks of cough, fever, and worsening dyspnea. She reported intermittent hemoptysis. On admission, she was hypoxic with exertion, had leukocytosis, and a minimally elevated D-dimer. CT revealed multifocal opacities and extensive centrilobular ground-glass nodules in multiple lobes, concerning for miliary TB. Repeat imaging showed progression, resulting in airborne isolation. Three acid-fast bacilli (AFB) smears and an Mycobacterium tuberculosis/Rifampin resistance (MTB/RF) assay were negative, and cultures remained negative after 8 weeks. Serologic testing showed elevated Immunoglobulin M (4.82 IU/mL) with low Immunoglobulin G, confirming active infection. She was treated with antibiotics and required supplemental oxygen. Notably, bronchospasm improved with Xopenex inhaler despite no prior history of asthma. She gradually improved and remained clinically stable at one month follow-up, with pulmonary function testing at four months showing continued recovery. Discussion This case highlights a highly atypical presentation of M. pneumoniae infection with hemoptysis and radiographic findings strongly suggestive of miliary TB. Misdiagnosis could have led to prolonged isolation and unnecessary TB therapy. To our knowledge, this is the first documented case of M. pneumoniae pneumonia mimicking miliary TB both clinically and radiographically. Due to M. pneumoniae’s ability to present as other types of infections, clinicians should consider M. pneumoniae serology in patients with diffuse pulmonary infiltrates and hemoptysis when TB is suspected but unconfirmed. Conclusion We present the first known case of a patient with Mycoplasma pneumoniae presenting TB-like symptoms with hemoptysis and miliary CT patterns. This case underscores the importance of including M. pneumoniae in the diagnosis of suspected miliary TB and highlights the value of serologic testing in guiding accurate diagnosis and management. This abstract is funded by: None