Snapshot An 18-year-old college student presents to the student health clinic with a mild fever, headache, fatigue, and a dry, non-productive cough. He says that his symptoms started about 3 weeks ago and have not improved. The physician obtains a chest radiograph, which shows a pattern of diffuse interstitial infiltrates that appears worse than the patient’s physical appearance. The patient is prescribed azithromycin for his infection. Introduction Classification Mycoplasma pneumoniae pleomorphic no cell wall cell membrane contains cholesterol causes an atypical “walking” pneumonia Epidemiology demographics more common in patients < 30 years of age risk factors frequently seen among young individuals living in close contact college students living in dormitories military recruits prisoners Pathogenesis transmission respiratory droplets Mycoplasma pneumoniae attaches to the respiratory epithelium, destroys the superficial layer of respiratory epithelial cells, and reduces the ability of the upper airways to clear themselves Associated conditions cold autoimmune hemolytic anemia erythema multiforme acute interstitial nephritis bacterial myocarditis Presentation Symptoms mild fever headache non-productive cough Physical exam non-productive cough bilateral wheezing may be heard on auscultation macropapular or vesicular rash Imaging Chest radiography patchy or diffuse interstitial infiltrates chest radiograph often looks more severe than the patient’s actual presentation Studies Labs detection of high titer of cold agglutinins (IgM antibodies) on serology cold agglutinin production peaks during the third week of infection Microbiological studies growth on Eaton agar not seen on Gram stain due to lack of a cell wall Making the diagnosis based on clinical presentation and laboratory studies Differential Viral infection distinguishing factor would not produce high titer of cold agglutinins (IgM) Chlamydophila pneumoniae infection distinguishing factor d3 cytoplasmic inclusions (reticulate bodies) seen on Giemsa or fluorescent antibody-stained smear Legionella infection distinguishing factor different demographic more common in smokers and patients with chronic lung disease grows on charcoal yeast extract agar buffered with cysteine and iron Treatment Medical macrolide antibiotics (especially Azithromycin) doxycycline fluoroquinolones Complications Autoimmune hemoltyic anemia Acute interstitial nephritis Bacterial myocarditis