Brown Sputum: Causes from Smoking to Serious Lung Disease
Brown or black-tinged sputum indicates old blood, tar, or pigment-laden macrophages. Always warrants clinical evaluation.
Common Causes
- Smoking: Tar and combustion products accumulate in macrophages → brown/black sputum. Chronic bronchitis component.
- Air pollution/occupational exposure: Dust, silica, coal (anthracosis), diesel exhaust.
- Chronic bronchitis (COPD): Persistent cough + sputum × 3 mo/yr × 2 yrs. Brown in smokers.
- Bronchiectasis: Chronic purulent sputum; brown during exacerbations or with old blood.
- Pneumonia: Klebsiella (currant jelly), Pseudomonas (green), anaerobes (foul, brown). Old blood from parenchymal breakdown.
- Pulmonary TB: Blood-tinged → brown sputum; night sweats, weight loss.
- Lung cancer: Hemoptysis → brown sputum; weight loss, new cough, risk factors.
- Pulmonary embolism (infarction): Hemorrhagic infarction → rusty/brown sputum.
- Fungal infection: Aspergillosis (brown plugs), allergic bronchopulmonary aspergillosis (ABPA).
Red Flags for Urgent Workup
- Hemoptysis (bright or dark blood)
- Weight loss, night sweats, fever
- New/worsening dyspnea
- Risk factors: smoking >20 pack-years, age >50, asbestos exposure
Diagnostic Approach
Sputum cytology (3 samples), culture (bacterial, fungal, AFB), CT chest, bronchoscopy if central lesion suspected.
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