Overview
Definition:
Mycoplasma pneumoniae is a bacterium that causes a spectrum of respiratory illnesses, most commonly "walking pneumonia" or primary atypical pneumonia
It lacks a cell wall, making it intrinsically resistant to beta-lactam antibiotics.
Epidemiology:
It is a common cause of community-acquired pneumonia (CAP) in children and adolescents, particularly during outbreaks that occur every 3-5 years
Transmission occurs through respiratory droplets
Peak incidence is in school-aged children and young adults.
Clinical Significance:
M
pneumoniae is a frequent pathogen responsible for significant morbidity in adolescents, often requiring medical attention and impacting school attendance
Understanding appropriate antibiotic choices is crucial for effective management and preventing complications, especially given antimicrobial resistance patterns.
Clinical Presentation
Symptoms:
Gradual onset of symptoms
Insidious development of cough, often non-productive initially, progressing to productive
Headache
Malaise
Low-grade fever
Sore throat
Nasal congestion
Extrapulmonary manifestations may include rash, myalgias, arthritis, or neurological symptoms.
Signs:
Fever, often low-grade
Pharyngitis
Nasal discharge
Non-specific pulmonary findings with variable auscultation findings, sometimes rhonchi or scattered crackles
Wheezing can occur
Pleural effusion is uncommon but possible
Vital signs are usually stable.
Diagnostic Criteria:
Diagnosis is often clinical, supported by laboratory findings
There are no pathognomonic signs or symptoms
Definitive diagnosis relies on serological testing (paired IgM and IgG antibodies), PCR, or culture, though these are not routinely used in initial clinical management.
Diagnostic Approach
History Taking:
Inquire about recent sick contacts, school attendance, and travel history
Onset and progression of respiratory symptoms
Presence of systemic symptoms like headache or myalgias
History of asthma or other chronic lung disease
Extrapulmonary symptoms.
Physical Examination:
Complete head-to-toe examination, focusing on respiratory system
Assess for pharyngeal erythema, nasal congestion, and lung auscultation for adventitious sounds
Palpate for lymphadenopathy
Examine skin for rashes
Assess for joint tenderness or swelling if arthritis is suspected.
Investigations:
Chest X-ray may reveal patchy infiltrates, interstitial or reticular patterns, or peribronchial thickening
it is often normal or shows minimal changes
Complete blood count (CBC) typically shows normal or mildly elevated white blood cell count without significant eosinophilia
Serological tests (e.g., complement fixation test, ELISA for IgM/IgG) can be performed but are retrospective
PCR on nasopharyngeal swabs can provide rapid diagnosis but is not widely available for routine use.
Differential Diagnosis:
Other causes of atypical pneumonia, including Chlamydophila pneumoniae, Legionella pneumophila, and viral pneumonias (influenza, RSV, adenovirus)
Bacterial pneumonias (Streptococcus pneumoniae) usually present with more acute onset and lobar consolidation
Non-infectious causes like reactive airway disease or early asthma exacerbation.
Management
Initial Management:
Supportive care is paramount
Ensure adequate hydration
Rest
Antipyretics (acetaminophen or ibuprofen) for fever and discomfort
Isolation is generally not necessary due to mild infectivity after treatment initiation.
Medical Management:
Antibiotic therapy is indicated to shorten illness duration and prevent complications
Macrolides are the preferred agents in adolescents
Azithromycin 10 mg/kg once daily for 3-5 days (maximum 500 mg/day)
Alternative macrolides: Clarithromycin 7.5 mg/kg twice daily for 7-14 days (maximum 500 mg/dose)
Erythromycin 10 mg/kg 4 times daily for 14 days (less preferred due to dosing frequency and GI side effects)
Tetracyclines (Doxycycline 4 mg/kg/day in 2 divided doses, maximum 100 mg/dose, for 7-14 days) are an alternative for adolescents >8 years old if macrolide resistance is suspected or macrolides are contraindicated/ineffective.
Surgical Management:
Not typically indicated for uncomplicated M
pneumoniae pneumonia
Rarely considered for severe cases with complications like empyema, which would then be managed by thoracic surgery.
Supportive Care:
Monitoring for signs of respiratory distress or worsening symptoms
Adequate fluid intake to prevent dehydration
Nutritional support as tolerated
Education on symptom management and follow-up.
Complications
Early Complications:
Extrapulmonary manifestations: Hemolytic anemia (cold agglutinins)
Neurological complications (encephalitis, meningitis, Guillain-Barré syndrome)
Cardiac involvement (myocarditis, pericarditis)
Dermatological complications (erythema multiforme, Stevens-Johnson syndrome)
Gastrointestinal issues
Severe pneumonia with respiratory failure requiring hospitalization and oxygen therapy.
Late Complications:
Persistent cough
Post-infectious reactive airway disease
Rarely, bronchiectasis or interstitial lung disease may be sequelae, though typically M
pneumoniae-associated pneumonia resolves completely.
Prevention Strategies:
Good respiratory hygiene practices, including handwashing and covering coughs/sneezes
Prompt diagnosis and appropriate antibiotic treatment can reduce transmission and severity
No vaccine is currently available.
Prognosis
Factors Affecting Prognosis:
Age
Presence of underlying chronic lung disease (e.g., asthma)
Severity of initial illness
Promptness of treatment
Development of complications.
Outcomes:
Prognosis is generally excellent with appropriate antibiotic therapy and supportive care in adolescents
Most children recover fully within a few weeks
Prolonged cough can occur in a minority of patients.
Follow Up:
Follow-up is typically not required for uncomplicated cases
Advise parents to seek medical attention if symptoms worsen or persist beyond expected duration
If complications arise, specific follow-up protocols will be required.
Key Points
Exam Focus:
M
pneumoniae is a leading cause of atypical pneumonia in adolescents
Antibiotics of choice are macrolides (azithromycin, clarithromycin)
Tetracyclines (doxycycline) are an alternative in adolescents >8 years
Lack of cell wall makes it resistant to beta-lactams
Extrapulmonary manifestations are common.
Clinical Pearls:
Suspect M
pneumoniae in adolescents with subacute onset of cough, pharyngitis, and low-grade fever, especially during community outbreaks
A normal or near-normal chest X-ray with significant symptoms should raise suspicion for atypical pathogens
Always consider extrapulmonary manifestations.
Common Mistakes:
Prescribing beta-lactam antibiotics which are ineffective
Delaying antibiotic treatment
Underestimating the potential for extrapulmonary complications
Not considering doxycycline in older adolescents when macrolides fail or are contraindicated.