Pneumonia, Mycoplasma

AUTHOR: Brian Block, MD

Definition

Mycoplasma pneumonia is an infection of the lung parenchyma caused by a small rod-shaped bacterium, Mycoplasma pneumoniae.

Synonyms

Primary atypical pneumonia

Walking pneumonia

Mycoplasma pneumonia

ICD-10CM CODE
J15.7		Pneumonia due to Mycoplasma pneumoniae

Epidemiology & Demographics

Incidence (in U.S.)

Frequent cause of community-acquired pneumonia (CAP); particularly in children and adults <40 yr
Causes periodic outbreaks with high secondary attack rate among household contacts because it is easily transmitted ¹
Many cases probably resolve without coming to medical attention ²
Asymptomatic carriage thought to be common

Predominant Sex

Equal distribution

Predominant Age

School-age children and young adults (ages 5 to 20 yr)³

Peak Incidence

Occurs throughout the year but outbreaks are more common in late summer and fall
Transmitted by respiratory droplets

Genetics

Familial disposition:

None known
May be more severe in patients with sickle cell anemia

Physical Findings & Clinical Presentation

Common symptoms include fever, cough, headache, and otalgia
Exam findings include rhonchi or rales, conjunctivitis, lymphadenopathy
Rash occurs in 10% to 25% of infected individuals, ranging from self-limited morbilliform eruptions to life-threatening rashes including Stevens-Johnson syndrome ⁴
Some patients develop autoimmune hemolytic anemia due to autoantibodies (cold agglutinins)
Neurologic manifestations are also possible but less common (mono- or polyneuritis, transverse myelitis, cranial nerve palsies)
Table E1 summarizes the clinical manifestations of Mycoplasma pneumoniae

Etiology

Spreads person-to-person via respiratory droplets with an incubation period of 1 to 3 wk

Diagnosis ⬆ ⬇

Differential Diagnosis

Typical bacterial pneumonia (S. pneumoniae, H. influenza)
Other causes of “atypical” pneumonia (Legionella, Chlamydophila)
Viral pneumonia (e.g., influenza, RSV, COVID-19)
Noninfectious causes of respiratory distress

Workup

Thorough history and physical examination
Chest x-ray (Fig. E1)

Laboratory Tests

White blood cells (WBCs):
1. WBC count >10,000/mm³ in approximately one fourth of patients
2. Leukopenia rare
Cold agglutinins:
1. Detected in approximately 50% to 70% of all patients within 1 to 2 wk of infection ⁵
2. Neither sensitive nor specific, so are of limited diagnostic utility. Cold agglutinins are also found in:
  1. Lymphoproliferative diseases
  2. Influenza
  3. Mononucleosis
  4. Adenovirus infections
  5. Legionella pneumonia
PCR has replaced serology as the test of choice to confirm the diagnosis
Serology and culture are other means of diagnosis, but culture is technically difficult, and results may take weeks
Mycoplasma cannot be seen on Gram stain because they lack a cell wall

Imaging Studies

Classically patchy, reticular opacities with lower-lobe predominance
Radiographic abnormalities frequently out of proportion to physical findings (Fig. E2)
Pleural effusions are seen in approximately 30% of patients, typically small
Potential findings in late-stage of infection or after acute infection resolves:
1. Lung abscess
2. Pneumatoceles
3. Lobar collapse
4. Hyperlucent lung syndrome (aka Swyer-James or postinfectious bronchiolitis)

Treatment ⬆ ⬇

Therapeutic considerations:
1. Therapy shortens illness duration, but the disease is self-limiting in most children and immunocompetent adults.
2. Given that mycoplasma has no cell wall, it is resistant to beta-lactam antibiotics.
3. Macrolide resistance is also a developing concern.⁶
Antimicrobial options:
1. Azithromycin: 500 mg daily × 3 days or 500 mg initially, then 250 mg daily for 4 days for adults. For children: 10 mg/kg in one dose initially, then 5 mg/kg daily for 4 days.
2. Clarithromycin: 500 mg bid for 10 days in adults, 15 mg/kg per day in two divided doses for 10 days in children.
3. Erythromycin (500 mg 4x per day) for adults or 30 to 40 mg/kg per day in four divided doses in children.
4. Doxycycline: 2 to 4 mg/kg per day in one or two divided doses for 10 days, maximum daily dose: 100 to 200 mg but contraindicated in young children or women of childbearing age.
5. Respiratory fluoroquinolones such as levofloxacin or moxifloxacin are alternatives for treatment in adults, but should not be used in young children.

Chronic Rx

Effective antimicrobial therapy does not eliminate the organism from the respiratory secretions, which may remain positive for weeks.
Serum antibody response does not necessarily provide lifelong immunity.

Disposition

Clinical improvement is almost universal within 10 days.
Chest imaging generally improves within 5 to 8 wk.
Person-to-person spread can be minimized by avoiding open coughing, especially in enclosed areas.
Azithromycin prophylaxis has efficacy in close contacts.⁷

Referral

To infectious disease specialist for patients not responding to treatment, for severe infection (including multilobar involvement), or for severe extrapulmonary manifestations
To pulmonologist, if diagnosis is unclear or alternate diagnosis being considered

TABLE E1 Clinical Manifestations of Mycoplasma Pneumoniae Infection

Respiratory tract		Pharyngitis, Laryngitis, Acute Bronchitis, Bronchopneumonia
Skin and mucosa		Maculopapular and vesicular exanthema, urticaria, purpura, erythema nodosum, erythema multiforme, Stevens-Johnson syndrome
Central nervous system		Meningitis, meningoencephalitis, acute psychosis, cerebellitis, Guillain-Barré syndrome ∗
Other organ involvement		Pancreatitis, diabetes mellitus, nonspecific reactive hepatitis, subacute thyroiditis ∗
Autoimmune and other phenomena		Hemorrhagic bullous myringitis, hemolytic anemia, pericarditis, thromboembolism ∗

^∗Some association remains uncertain.

From Cohen J, Powderly WG: Infectious diseases, ed 2, St Louis, 2004, Mosby.

Figure E1 Radiographic findings in Mycoplasma pneumoniae pneumonia are nonspecific.

Bilateral bronchopneumonia occurred in this patient.

From Mason RJ et al: Murray and Nadel’s textbook of respiratory medicine, ed 5, Philadelphia, 2010, Saunders.

Figure E2 Localized airspace opacification resulting from Mycoplasma pneumoniae.

From Specht N [ed]: Practical guide to diagnostic imaging, St Louis, 1998, Mosby.

Pearls & Considerations ⬆ ⬇

Comments

Outbreaks occur in military recruits, group homes, nursing homes, and in the community.
Infection control: In the hospital these patients should be on droplet precautions.
Chest x-ray resolution is complete by 8 wk in approximately 90% of patients.

Related Content

Mycoplasma Pneumonia (Patient Information)

Pneumonia, Bacterial (Related Key Topic)

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Basic Information ⬇

Diagnosis ⬆ ⬇

Treatment ⬆ ⬇

Pearls & Considerations ⬆ ⬇

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