Which organism is a common cause of atypical pneumonia in school-age children?

• A. Streptococcus pneumoniae
• B. Haemophilus influenzae
• C. Mycoplasma pneumoniae
• D. Staphylococcus aureus

Answer: (C)

In school-age children, atypical pneumonia is most commonly caused by Mycoplasma pneumoniae. This organism tends to produce a milder, more gradual illness than typical bacterial pneumonia, with symptoms like a dry, nonproductive cough, low-grade fever, malaise, headache, and sometimes sore throat or conjunctivitis. Chest imaging often shows diffuse interstitial or patchy infiltrates rather than a single lobar consolidation.

A key point is that Mycoplasma lacks a cell wall, so it does not respond to beta-lactam antibiotics and isn’t easily seen on Gram stain or routine culture. Diagnosis is usually made by clinical picture supported by PCR or serology. Treatment with a macrolide (such as azithromycin or clarithromycin) is typically effective in children; doxycycline is an option in older children when appropriate.

By contrast, typical pneumonia causes in this age group, like Streptococcus pneumoniae, usually present with abrupt fever and productive cough and show lobar consolidation on imaging, while Haemophilus influenzae and Staphylococcus aureus have their own patterns and contexts. The combination of the school-age pattern, the distinctive mild, insidious presentation, and the interstitial radiographic findings points most clearly to Mycoplasma pneumoniae.