Mycoplasma Pneumonia On the Rise

AUTHORS:

Kelly Tran, DO; Zachary Gohsman, MD
University of Florida, Gainesville, Department of Pediatrics

CASE REPORT | PUBLISHED Fall 2025 | Volume 45, Issue 4

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Abstract

Mycoplasma infections have been on the rise in the United States since spring of 2024. Notably, children under five years of age are being affected more than before. Symptoms are usually mild, self-limited, and typically include fever, cough, runny nose, and sore throat. Diagnosis can be made clinically or confirmed by respiratory panels. First-line treatment includes macrolides; although, doxycycline and fluoroquinolones can also be used. Providers should consider Mycoplasma if patients fail empiric treatment of community-acquired pneumonia with beta-lactams like amoxicillin.

Introduction

Cases of Mycoplasma pneumoniae pneumonia, also known as “walking pneumonia” or atypical pneumonia, have been on the rise since spring of 2024 in both adult and pediatric populations1.

Case Presentation

A five-year-old male with no significant past medical history presents to the emergency department with shortness of breath following three days of worsening cough, fever and decreased activity. He was seen two days prior to presentation by his pediatrician and was diagnosed with community-acquired pneumonia. He was given a prescription for high-dose amoxicillin (45 mg/kg twice daily) and patient was adherent with medication. His symptoms did not improve. He returned to the emergency department (ED) because he was noted to be breathing “heavily.”

In the ED, his temperature was 101° F, a heart rate of 120/minute, and a respiratory rate of 38/minute. His oxygen saturation was 87% in room air. Physical exam was remarkable for decreased breath sounds bilaterally in the  lung bases, with scattered crackles and wheezes. He was able to say 3-4 words between episodes of coughing. The remainder of his physical exam was unremarkable. A chest X-ray showed patchy areas of consolidation and perihilar infiltrates.

He was placed on two liters of oxygen via low flow nasal cannula which improved his oxygen saturations to 90-94%. He was given acetaminophen for his fever, IV Ampicillin/Sulbactam (Unasyn® 300 mg/kg/day divided every 6 hours) was started and patient was hospitalized. On day two of hospitalization, after receiving three doses of IV Ampicillin/Sulbactam, he was not improving and continued to need supplemental oxygen. His physical exam remained unchanged. Due to the lack of improvement and findings of diffuse crackles and wheezes on physical exam, M. pneumoniae infection was suspected. A respiratory pathogen panel was performed and was reported positive for M. pneumoniae. He was started on azithromycin (10 mg/kg). By day 3, he was weaned off supplemental oxygen as his respiratory symptoms improved. He was discharged home with instructions to complete azithromycin for a total five-day course.

Discussion

Once regarded as an infection that primarily affected school-aged children and adolescents, M. pneumoniae pneumonia is now being seen more frequently in infants and toddlers. Data collected from the Center of Disease Control (CDC) show that from January 2024 to November 2024, the discharge diagnosis of M. pneumoniae infections increased from 0.4% to 7.6% in children ages 0-1, from 0.3% to 7.0% in children ages 2-4, and from 2.2% to 7.6% in children ages 5-17.1 In 2024, the diagnosis of M. pneumoniae infections peaked in August in children ages 2-4 and 5-17. However, at the time of writing this article, the diagnosis of M. pneumoniae infections is peaking in some of the most vulnerable children, infants ages 0-1 year of age. Given these increasing numbers, it is important for clinicians to be familiar with the epidemiology, presentation, diagnosis, and treatment of M. pneumoniae infections, including pneumonia.

Epidemiology

Mycoplasma pneumoniae is a bacterium that causes an atypical community-acquired pneumonia. It is transmitted via respiratory droplets with outbreaks occurring in places with close contact including schools, college dorms, prisons, nursing facilities, hospitals, and military barracks. It affects all age groups but most commonly affects children ages 5-17. About 2 million infections occur each year in the United States, though many infections go undetected due to lack of point-of-care testing and mild clinical presentation.2 Per CDC data, since Spring 2024, the number of positive tests has increased from 0.7% to 3.3% for all age groups.1 The best methods for preventing the spread of M. pneumoniae are appropriate hand-washing, good cough etiquette by covering mouth and nose when coughing or sneezing, and wearing masks.

Presentation

Infection with M pneumoniae is usually mild and self-limiting. The incubation period ranges from 1-4 weeks, which is longer than for most pathogens. Symptoms of infection are non-specific and can include, but are not limited to: fever, rhinorrhea, cough, pharyngitis, tracheobronchitis, otalgia, headache, and malaise. Cough can persist for 3 to 4 weeks, which can be distressing to children and their families.3 Extrapulmonary manifestations include erythema multiforme4 and reactive infectious mucocutaneous eruptions (RIME)5, hemolysis due to IgM cold agglutinins2, arthralgias6, and GI disturbances. Cardiac manifestations include pericarditis, myocarditis, endocarditis, and cardiac tamponade.7 Another disease process caused by M. pneumoniae that has garnered attention is Mycoplasma-induced Acute Disseminated Encephalomyelitis (ADEM).8,9

Physical exam findings are non-specific and can include scattered rales and wheezes or decreased aeration throughout lung fields. Some extrapulmonary physical exam findings include oropharyngeal erythema, erythematous maculopapular rash, and bullous myringitis.

Diagnosis

Diagnosis of M. pneumoniae pneumonia is mostly made in the outpatient setting based on history and physical exam. It is often diagnosed after there is lack of improvement on empiric treatment of community-acquired pneumonia with beta-lactams such as amoxicillin. There is no approved point-of-care testing for M. pneumoniae in the United States. However, it is included on many respiratory pathogen panels that utilize PCR testing. These tests are more commonly used in EDs and hospitals. The remainder of the bloodwork may be normal, or it may show hemolysis, and/or there may be elevated inflammatory markers such as CRP or procalcitonin. Given that many of the laboratory findings are non-specific or may not be present, labs tests are not usually required to make the diagnosis. Chest x-ray findings are also non-specific and not necessary for diagnosis. The most common chest x-ray findings are unilateral or bilateral patchy areas of air-space opacification or a diffuse reticulonodular pattern.10

Treatment

Antimicrobial treatment is not necessary in all cases of M.  pneumoniae pneumonia. When antimicrobial treatment is needed, macrolides, most commonly azithromycin, are the first-line treatment. Mycoplasma pneumoniae does not have a cell wall, which makes it resistant to beta-lactam antibiotics that act by disrupting cell wall synthesis.2 Fortunately, macrolide resistance remains low in the United States; especially compared to other parts of the world such as Asia.11 Though not commonly used in pediatrics due to their side effect profiles, doxycycline and fluoroquinolones can also be used for treatment of M. pneumonie infections. Supportive care should also be encouraged.

References

  1. Centers for Disease Control and Prevention. Mycoplasma Pneumoniae Infections Have Been Increasing. https://www.cdc.gov/ncird/whats-new/mycoplasma-pneumoniae-infections-have-been-increasing.html. Accessed December 1, 2024.
  2. Waites KB, Xiao L, Liu Y, Balish MF, Atkinson TP. Mycoplasma pneumoniae from the Respiratory Tract and Beyond. Clin Microbiol Rev. 2017;30(3):747-809.
  3. Foy HM. Infections caused by Mycoplasma pneumoniae and possible carrier state in different populations of patients. Clin Infect Dis. 1993;17 Suppl 1:S37-S46.
  4. Ricles V, Ahmed S, Trautz A, Braden MM, Erickson-Parsons L, Krakowski AC. Erythema Multiforme in a Child with Mycoplasma-Associated Infection. J Pediatr. 2023;257:113373.
  5. Pan CX, Hussain SH. Recurrent reactive infectious mucocutaneous eruption: A retrospective cohort study. J Am Acad Dermatol. 2023;89(2):361-364. doi:10.1016/j.jaad.2023.03.027
  6. Mărginean CO, Georgescu AM, Meliţ LE. Arthritis associated with Mycoplasma pneumoniae in a pediatric patient: A case report. Medicine (Baltimore). 2021;100(2):e24316.
  7. Asif M, Chaudhry HS, Aslam S, Nadeem I, Chaudhry SS, Khan W. Heart Failure Associated With Mycoplasma Pneumoniae Infection, A Case and Review of Literature. J Community Hosp Intern Med Perspect. 2023;13(3):55-58. Published 2023 May 8.
  8. Kang S, Lee BL. A Case of Acute Disseminated Encephalomyelitis Accompanying Intussusception Associated with Mycoplasma pneumoniae Infection. Ann Child Neurol. 2023;31(2):133-136.
  9. Laila A, El-Lababidi RM, Hisham M, Mooty M. A case of acute disseminated encephalomyelitis following Mycoplasma pneumoniae infection. IDCases. 2018;12:41-43. Published 2018 Mar 12.
  10. Reittner P, Müller NL, Heyneman L, et al. Mycoplasma pneumoniae pneumonia: radiographic and high-resolution CT features in 28 patients. AJR Am J Roentgenol. 2000;174(1):37-41.
  11. Waites KB, Ratliff A, Crabb DM, Xiao L, Qin X, Selvarangan R, Tang YW, Zheng X, Dien Bard J, Hong T, Prichard M, Brooks E, Dallas S, Duffy L, Mixon E, Fowler KB, Atkinson TP. Macrolide-resistant Mycoplasma pneumoniae in the United States as determined from a national surveillance program. J Clin Microbiol. 2019;57(11):e00968–19.

Disclosures: Authors report no conflicts of interest.