Pneumonia: Diagnostic workup to rule out mimics

When suspected acute bacterial Pneumonia fails to respond to empiric antibiotic therapy, expand your differential diagnosis to include noninfectious conditions that can mimic pneumonia, particularly if extrapulmonary organs are prominently involved or the radiographic pattern is unusual. First, consider common pneumonia mimics, such as pulmonary thromboembolism and congestive heart failure. Pulmonary thromboembolism can cause spiking fever; dyspnea; tachycardia; hypoxemia; and nonspecific chest radiographic abnormalities, such as atelectasis, parenchymal consolidation, and small pleural effusion. Cardiogenic pulmonary edema from cardiac pump failure or mitral stenosis may produce frothy sputum mixed with blood and a patchy infiltrate. Always evaluate persistent volume loss or recurrent pneumonia in the same area of the lung to rule out obstructing lesions. Antinuclear antibody and anti-double stranded DNA antibody assays help distinguish lupus pleuropulmonary disease.