Mycoplasma infection mimicking hypersensitivity pneumonitis.

Mycoplasma pneumoniae infection is a common cause of community-acquired pneumonia.’ It may cause a dry cough, dyspnea, and an interstitial infiltrate on chest radiography. Hypersensitivity pneumonitis may present with similar symptoms and radiologic features.’ We recently cared for a 46-year-old ex-smoker who presented with dyspnea, a dry cough, and malaise of 3 weeks’ duration. Treatment with amoxicillin had failed to improve his condition. Six months previously he had obtained a budgerigar, which he kept in his kitchen. On physical examination he looked relatively well, was afebrile, and had bilateral fine inspiratory crepitations. There were no other findings. A chest radiograph and computed tomographic scan revealed a bilateral patchy reticulonodular pattern. Findings from a full blood examination were normal. His PaO2while breathing air was 58 mm Hg. Fiberoptic bronchoscopy, transbronchial biopsy, and bronchoalveolar lavage revealed mild nonspecific interstitial inflammatory changes and marked lymphocytosis in the lavage fluid (49 percent of cells obtained). Precipitins for budgerigar extract were negative. His atypical pneumonia serology later showed the presence of anti-Mycoplasma 1gM . A diagnosis of resolving Mycoplasma pneumonitis was made. Despite a computerized search of the literature, we were unable to find any previous reports of bronchoalveolar lavage findings following Mycoplasma infection. Our finding of marked lymphocytosis in resolving Mycoplasma pneumonitis is important because it alerts clinicians to the possibility of confusing this infection with other relatively common conditions (hypersensitivity pneumonitis, in our case) that are associated with lavage lymphocytosis. It also emphasizes the need to exclude atypical infections in any patient presenting with a subacute illness associated with physical examination and radiologic findings suggestive of pneumonitis.