Snapshot A 37-year-old man presents to his primary care physician with subjective fever, malaise, and cough. He reports a few episodes of night sweats and has noted an unintentional 15-pound loss over the course of 2 months. Yesterday, he noted bloody sputum. He recently immigrated from Central Africa and currently lives with many family members in a small apartment. Chest radiograph demonstrates a cavitary lesion in the right upper lobe of the lung. Introduction Definition infection of the respiratory system caused by Mycobacterium tuberculosis Transmission inhaling airborne particles (droplet nuclei) suspected patients should be placed on respiratory isolation precautions during workup Extrapulmonary Tb meningitis Pott disease (vertebral infection) miliary Tb pericarditis adrenal gland infection genitourinary Tb Epidemiology Risk factors close contact with someone with tuberculosis (Tb) e.g., prisons and homeless shelters immigrating from highly endemic regions such as Bangladesh Cambodia Central African Republic working in hospitals and nursing homes immunosuppression (e.g., HIV, diabetes, and on immunosuppressive medications) substance use disorder most important for diffuse reticulonodular pattern Etiology Pathophysiology droplet nuclei produced by coughing gets inhaled → recruits macrophages when in the alveoli → dissemination of macrophage infected cells into deeper tissues and caseating granuloma formation Mycobacterium tuberculosis Presentation Symptoms cough (productive or nonproductive) hemoptysis night sweats fever loss of appetite Physical exam weight loss although physical exam is not helpful in diagnosing Tb, it is important to assess for extrapulmonary involvement e.g., hepatosplenomegaly, lymphadenopathy, scrotal, and pelvic tenderness Imaging Chest radiography findings non-specific findings (e.g., patchy or lobar consolidation or non-detectable lesions) cavitary lesions miliary nodules hilar adenopathy pleural effusion Studies Sputum specimen acid-fast bacilli culture nucleic acid amplification tests Blood interferon-gamma release assay Tuberculin skin test results in a delayed immune response with the administration of purified protein derivatives (PPD) from Mycoplasma tuberculosis measured in 48-72 hours Findings ≥ 5 mm considered a positive test in patients with HIV recent Tb exposure chest radiographic findings consisted of healed Tb infection organ transplantation or on immunosuppressants ≥ 10 mm considered a positive test in patients with injection drug users chronic diabetes chronic renal failure employees in high-risk settings (e.g., physicians, nurses, or prison workers) recent immigrant from endemic country ≥ 15 mm considered a positive test in patients with no known risk factors Treatment Medical rifampin, isoniazid, pyrazinamide, and ethambutol (RIPE) therapy indication treatment of choice for the 2-month initial phase 4-month continuation phase is with rifampin and isoniazid side effects isoniazid should be given with vitamin B6 (pyridoxine) to prevent peripheral neuropathy B6 deficiency can cause refractory seizures treat with pyridoxine rifampin, isoniazid, and pyrazinamide can cause liver toxicity ethambutol results in optic neuropathy rifampin causes reddish-orange discoloration of body secretions pyrazinamide causes hyperuricemia, which can precipitate gouty attacks isoniazid indication for Tb prophylaxis Complications Tuberculoma Aspergilloma Acute respiratory failure