Mycoplasma are small bacteria that do not contain a cell wall. They are difficult to grow in culture media and their growth is slow. The are unidentifiable in gram stains of sputum samples. 

Epidemiology

1. The incubation period is 1-3 weeks.
2. They are spread by large particles by aerosol to close contacts. The spread is increased within closed settings. 
3. The incidence of infection is greatest in older children, adolescents, and young adults. The increase utilization of daycare facilities, has lowered the age of susceptible children. 

1. The Mycoplasma organism produces a protein that allows attachment to a receptor on the respiratory epithelium. This complex induces an antibody response, the cold agglutinin. These antibodies will react with the I antigen of RBC glycoproteins. They will be detected one week after infection and may last for six weeks. The height of the titer may correlate with the seriousness of the illness. 
2. Mycoplasma will induce damage to respiratory epithelium from the trachea to bronchioles. 
3. Manifestations of illness are mostly confined to the respiratory system, but some cases are associated with extrapulmonary involvement. 

1. May not be preceding upper respiratory symptoms such as cold symptoms or rhinorrhea
2. May begin with headache, malaise, fever, and pharyngitis
3. Large airways initially involved producing cough and hoarseness. |
4. Progression to bronchopneumonia with persistence of cough and possible dyspnea. Will resolve in 3-4 weeks without treatment
5. Acute otitis media and sinusitis are unusual.
6. Radiographic findings
1. multifocal, bilateral diffuse infiltrates most frequent
2. occasionally have lobar pneumonia picture.
3. Pleural effusions are not rare
4. The xray often looks worse than the clinical picture. 
7. Typically there is no elevation of WBCs or increase of neutrophils or bands.
8. Mycoplasma infections are frequent triggers of reactive airway disease (asthma)
9. Extrapulmonary symptoms are thought to be autoimmune induced and include rashes, Stevens Johnson Syndrome, meningoencephalitis, arthritis, gastrointestinal symptoms.
10. Differential Diagnosis
1. Viral infections- adenoviruses, parainfluennza, influenza
2. Chlamydia pneumonia
3. Legionnaire's disease
4. Bacterial pneumonias
11. Diagnosis
1. Cold agglutinin titers >1/64 are found in adolescents and adults in approximately 50% of cases. This test is not reliable in children < 12 years of age. Difficult test to perform and should be limited to diagnose older patients. Other atypical pneumonias may induce low titers of cold agglutinins. 
2. CF titers- Difficult to perform and must demonstrate rising and falling titers.
3. IgM- must wait until 8-10 days of illness before detected, therefore not clinically helpful in most situations.
4. PCR- not readily available
5. Presence of polys in sputum without organism is suggestive of Mycoplasma infection.
12. Treatment - suggest to treat for 7-10 days
1. Erythromycin-( estolate or ethylsuccinate or stearate.) Will also be effective against other community acquired infections such as pneumococcal pneumonia.
2. Clarithromuycin and Azithromycin ( more expensive)
3. Tetracylcines in patients > 10 years old
4. May isolate organism for months after treatment.

1. Cimolai N. Mycoplasma pneumoniae Respiratory Infection. Pediatrics in Review. 1998;19:327-332. 
2. Kim CK et al. Late Abnormal Findings on High-Resolution Computed Tomography after Mycoplasma Pneumonia. Pediatrics. 2000; 105(2):372-378.