TB Determined: A Case of Pleural Mycobacterium Tuberculosis Confounded by Negative Acid-fast Bacillus Staining and Mycoplasma Co-infection

Abstract Pulmonary tuberculosis (TB) remains a public health concern in the U.S., though its incidence has declined in recent decades. Certain populations, including those from high-prevalence regions or with compromised immune systems, are at continued risk. Early recognition and diagnosis are crucial to prevent transmission and reduce morbidity and mortality. We present a case of pleural TB in a 31-year-old female with no significant medical history who presented with worsening dyspnea, persistent cough, fever, and chills for one month. Initially, she experienced right-sided pleuritic chest and back pain along with a dry cough. Despite antibiotic treatment for suspected community-acquired pneumonia, her symptoms worsened. She reported a 10-pound weight loss but denied night sweats or hemoptysis. Originally from Ecuador, she has lived in Queens, New York since 2019 where she works in a supermarket packing fresh produce. She denied ever being tested for TB and denied known TB contacts. In the emergency department, she was hypoxic and met sepsis criteria with a fever of 101.7°F, tachycardia, and tachypnea. CT scan revealed a large, partially loculated pleural effusion with right apical opacity, and ultrasound showed septated pleural fluid. The patient was admitted to ICU for sepsis due to suspected parapneumonic effusion. Empiric broad spectrum antibiotics were started, and a chest tube was placed. Pleural fluid analysis showed an exudative effusion with 96% lymphocytes and ADA level of 40 U/L. However, three consecutive sputum specimens stained negative for acid-fast bacillus (AFB) and MTB-PCR of pleural fluid was negative. Interestingly, Mycoplasma IgM was positive which confounded interpretation of fluid studies as mycoplasma parapneumonic effusions (MPPE) are typically lymphocyte predominant with literature reporting that ADA levels below 40 U/L virtually rule out TB and favor MPPE. Azithromycin was added, however the patient continued to have high fevers. Repeat chest CT revealed a more classically cavitated appearance of the right apical opacity with involvement of thickened pleura. Based on these findings and high clinical suspicion we opted to switch to RIPE therapy despite negative AFB staining. The patient eventually underwent VATS with pleural biopsy. She improved clinically and was able to be discharged back to the community with continued treatment. It was not until many weeks later that sputum and pleural biopsy cultures finally grew Mycobacterium tuberculosis. This case illustrates the potential complexity and lengthy time to definitive diagnosis of pleural TB and emphasizes the importance of clinical suspicion in initiating prompt treatment.