Although individual clinical features are not sufficiently distinctive to distinguish Legionnaires’ disease from other types of community-acquired pneumonia, there is a characteristic clinical profile that increases the likelihood of the diagnosis. It has been reported that encephalopathy, hyponatremia, microscopic hematuria, liver or renal function abnormalities occur more often in Legionnaires’ disease than in other types of pneumonia. In our series, patients with Legionnaires’ disease were more likely to have had antibiotics before admission, had mucosal sputum, gastrointestinal and neurologic symptoms and abnormalities in liver and renal function more frequently that those with pneumococcal pneumonia and there were no differences in the incidence of hyponatremia.
There are no differences in the initial radiologic patterns between Legionnaires’ disease and other types of community-acquired pneumonia. Only radiologic progression with multilobe involvement during the first hours after admission was seen more frequently in Legionnaires’ disease than in pneumonia caused by other germs. The most common complication is respiratory failure. Half of the patients with Legionnaires* disease developed it.