Clues Pointing TO This Diagnosis

Persistent cough lasting more than 2–3 weeks (three months here) — a cough >2–3 weeks is the cardinal trigger to investigate pulmonary TB
Hemoptysis (coughing up blood) — a classic sign of cavitary pulmonary TB
Drenching night sweats — a hallmark constitutional symptom of active TB
Unintentional weight loss with reduced appetite — constitutional wasting typical of active TB
Newly positive tuberculin skin test (conversion from prior negative) — documents new M. tuberculosis infection and raises suspicion for progression to disease
Healthcare-worker occupational exposure over decades — an established TB risk factor supporting the diagnosis
Upper-lobe infiltrate with cavitation on chest radiograph — the classic radiographic pattern of reactivation pulmonary TB in immunocompetent adults
Positive acid-fast bacilli (AFB) sputum smear — indicates mycobacteria and infectiousness pending culture confirmation
Sputum sent for AFB culture — culture confirms M. tuberculosis and provides drug susceptibilities
Symptomatic and radiograph-abnormal (versus asymptomatic latent infection) — the combination of symptoms, abnormal imaging, and positive smear distinguishes active TB disease from LTBI

Why It's NOT the Similar Diseases

NOT community-acquired bacterial pneumonia — that is acute over days with high fever and lobar consolidation that responds to standard antibiotics, not a 3-month course with night sweats, weight loss, hemoptysis, and upper-lobe cavitation
NOT lung cancer — although it can cause weight loss and hemoptysis, Edna has a newly positive TST, a positive AFB smear, and upper-lobe cavitary disease confirming a mycobacterial infection
NOT latent TB infection — LTBI is asymptomatic with a normal chest radiograph and negative smear/culture, whereas Edna is symptomatic with cavitation and a positive smear (active disease)
NOT COPD exacerbation — that features increased dyspnea, wheeze, and sputum in a smoker without cavitation, positive AFB smear, or TST conversion
NOT a lung abscess — that typically causes foul-smelling sputum with an air-fluid–level cavity in dependent segments, not apical cavitation with a positive AFB smear and TST conversion

Differential Diagnosis List

Community-acquired pneumonia — ruled out by the subacute 3-month course, TST conversion, positive AFB smear, and upper-lobe cavitation
Lung cancer — ruled out by newly positive TST and positive AFB smear/culture confirming M. tuberculosis
Latent TB infection — ruled out by presence of symptoms, an abnormal chest radiograph, and a positive smear
COPD exacerbation — ruled out by cavitary apical disease and microbiologic confirmation of mycobacteria
Lung abscess — ruled out by apical (rather than dependent) cavitation and positive AFB smear

Key Distinguishing Test

Sputum studies are confirmatory: at least three specimens for AFB smear microscopy, a nucleic acid amplification (molecular) test, and mycobacterial culture; culture growth of M. tuberculosis definitively confirms active pulmonary TB and provides drug-susceptibility results.
Chest radiography showing upper-lobe infiltrates with cavitation supports the diagnosis, and drug-susceptibility testing is performed on all positive cultures.

Board Note

Suspect pulmonary TB in anyone with cough >2–3 weeks plus compatible features (hemoptysis, fevers, night sweats, weight loss), especially with risk factors such as healthcare/occupational exposure, immigration from high-prevalence regions, HIV, homelessness, or incarceration
Standard treatment for drug-susceptible TB is the RIPE regimen: a 2-month intensive phase of isoniazid, rifampin, pyrazinamide, and ethambutol, then a 4-month continuation phase of isoniazid plus rifampin (6 months total)
A newer 4-month regimen (isoniazid, rifapentine, moxifloxacin, and pyrazinamide) is a conditionally recommended alternative for eligible patients ≥12 years with drug-susceptible pulmonary TB
Give pyridoxine (vitamin B6) with isoniazid to prevent peripheral neuropathy in at-risk patients (e.g., older adults, diabetics, pregnant, malnourished, HIV, alcohol use)
Know key drug toxicities: isoniazid → hepatitis and peripheral neuropathy; rifampin → hepatitis, orange-red body fluids, and many drug interactions (lowers levels of oral contraceptives, warfarin, etc.); pyrazinamide → hepatotoxicity and hyperuricemia; ethambutol → optic neuritis (check color vision and acuity)
Public health essentials: TB is reportable, manage with the health department, use directly observed therapy, place hospitalized patients in airborne (negative-pressure) isolation, perform contact investigation, and monitor sputum smears/cultures monthly until two consecutive cultures are negative

“Edna’s Story”