M. pneumoniae is a common cause of pneumonia. The diagnosis is suspected when the patient presents with symptoms suggesting primary atypical pneumonia including cough, fever, chills, headache, and malaise in association with a segmental or subsegmental pulmonary infiltrate(s), the white blood cell count is normal or only slightly elevated, and the Gram stain of the sputum (if any can be obtained) reveals polymorphonuclear leukocytes and few bacteria. The diagnosis is more difficult when the patient presents with symptoms not suggestive of pneumonia including lethargy, dyspnea, and a 1- to 4-week history of shortness of breath without cough or fever in association with diffuse reticulonodular or interstitial pulmonary infiltrates. The disease in the previously healthy host is usually benign and self-limiting. However, the course is shortened by the administration of tetracycline derivatives or erythromycin. M. pneumoniae pneumonia can occur in association with other diseases including sickle cell anemia, sarcoidosis, systemic lupus erythematosus, Hodgkin's disease, and various other immunodeficiency states. In these patients mycoplasma pneumonia can be very serious. Although there is no pathognomonic clinical or radiographic presentation, careful consideration of epidemiologic, clinical, laboratory, and radiographic data are usually sufficient to suggest the diagnosis in most patients.