The atypical pneumonias: a diagnostic and therapeutic approach.

Mycoplasmal pneumonia, tularemic pneumonia, Q fever pneumonia, psittacosis, and Legionnaires' disease are the most frequently encountered treatable atypical pneumonias. Mycoplasmal pneumonia, the most common, is often accompanied by nonexudative pharyngitis, conjunctivitis, or otitis. The nonproductive cough is characteristic. Tularemic pneumonia is characterized by substernal chest pain, bloody pleural effusion, and bilateral hilar adenopathy. Although the clinical presentation is mild, roentgenographic findings are impressive. Q fever pneumonia resembles psittacosis but is less serious; it may be accompanied by subacute bacterial endocarditis, hepatitis, or both. Psittacosis is characterized by prominent headache, bloody sputum, and relative bradycardia. Tetracycline is the drug of choice for either. In Legionnaires' disease, pneumonia is accompanied by prominent extrapulmonary symptoms. The most important diagnostic clues include diarrhea and mental confusion. Relative bradycardia and laboratory abnormalities are also helpful. Erythromycin is the drug of choice unless doubt exists as to the diagnosis.