An 18-year-old college student presents to her family physician with a non-productive cough and low-grade fevers for the past 3 weeks. She reports that several people in her dorm have been coughing as well. She is previously healthy and does not have any significant past medical history. She has not taken anything for the cough. On physical examincation, the patient's temperature 99.5° F (37.5° C) and auscultation of the lungs reveals no crackles, rhonchi or wheezing. COVID testing is negative. A chest x-ray demonstrates interstitial pulmonary infiltrates more severe than the patient's presentation suggests.
Which of the following is the most likely causative organism in this patient's illness?
D) Mycoplasma pneumoniae
Mycoplasma pneumoniae is the most common cause of interstitial (atypical) pneumonia. Interstitial pneumonia often presents with a more indolent course, including chronic cough and low-grade fever. Typically, chest x-ray reveals findings worse than expected based on clinical findings. Mycoplasma pneumoniae often breaks out in environments where people live in close quarters, such as college dormitories, military barracks, or prisons. Chlamydia and Legionella can also cause interstitial pneumonia, but Mycoplasma pneumoniae is the most common cause. Streptococcus pneumoniae is the most common cause of community acquired pneumonia, but usually produces lobular pneumonia, not interstitial pneumonia. Mycobacterium tuberculosis should be suspected when there is persistent cough, lymphadenopathy, fevers, night sweats, or weight loss and relevant risk factors such as potential tuberculosis exposure. The classic radiographic presentation of reactivation pulmonary tuberculosis is focal infiltration in the upper lobes with or without cavitation.
Key Learning Point
Mycoplasma pneumoniae is the most common cause of interstitial (atypical) pneumonia. Interstitial pneumonia often presents with a more indolent course, including chronic cough, and low-grade fever. Typically, chest x-ray reveals findings worse than expected based on clinical findings.
