Lung infiltrates are associated with which conditions?

• A. Pneumonia, tuberculosis, and nocardiosis
• B. Asthma and COPD
• C. Pulmonary embolism
• D. Pulmonary edema

Answer: (A)

Lung infiltrates on imaging reflect inflammatory or infectious material filling the airspaces or thickening the lung interstitium, often from processes that cause consolidation or nodular inflammation. The combination of pneumonia, tuberculosis, and nocardiosis is a classic trio that fits this pattern well. Pneumonia involves bacteria or other pathogens filling the alveoli with pus and fluid, producing focal or multilobar infiltrates. Tuberculosis creates granulomatous inflammation with patchy infiltrates and nodules, frequently in the upper lobes and sometimes with cavitation. Nocardiosis, an opportunistic infection, can produce pulmonary infiltrates and nodules that may cavitate, especially in individuals with weakened immune defenses.

Asthma and COPD are primarily airway diseases; their imaging typically shows airway thickening, mucus plugging, or hyperinflation rather than focal infiltrates. Pulmonary embolism may have normal imaging or show infarct-related changes that are not classic infiltrates. Pulmonary edema can cause diffuse interstitial or alveolar opacities that resemble infiltrates, but the hallmark in this context is infectious/inflammatory consolidation like pneumonia, TB, and nocardiosis.