Clinical Features and Complications

A doctor examines a college-aged woman with a stethoscope.

Mycoplasma pneumoniae infections cause a wide array of non-specific symptoms.

Clinical features

Mycoplasma pneumoniae infections can occur in the upper or lower respiratory tract. The bacteria can cause a wide array of extrapulmonary manifestations without obvious respiratory disease. Therefore, patients may have highly variable presentations.

Common manifestations

Infection most commonly results in:

  • Tracheobronchitis
  • Pharyngitis
  • Pneumonia
Common symptoms
  • Malaise
  • Fever
  • Cough
  • Headache

Illness onset can be gradual and subacute, slowly progressing to a higher fever and a persistent cough.

While the disease can persist for weeks or months, it is frequently mild and self-resolving. The organism may persist for several weeks in the oropharynx despite completion of recommended antimicrobial therapy and resolution of clinical symptoms.

Pneumonia symptoms

M. pneumoniae pneumonia is often referred to as “walking pneumonia”.

In addition to tracheobronchitis symptoms, pneumonia symptoms can include mild dyspnea. While the cough is initially dry, it may later produce moderate amounts of non-bloody sputum.

In addition, chest auscultation may show scattered or localized rhonchi and expiratory wheezes. Chest radiograph often shows unilateral or bilateral bronchopneumonia.

Younger patients may have different manifestations, symptoms

Younger patients often manifest with different clinical characteristics than patients over 5 years of age. For example, infections in younger patients may run subclinical, be mild, and not result in pneumonia. Infections in younger patients are often characterized by coryza and wheezing without concomitant fever, and sometimes include diarrhea and vomiting.

Clinical complications

Severe complications are uncommon, but can result in hospitalization and sometimes death.

Complications involving the respiratory system include exacerbation of asthma and severe pneumonia.

Complications include:

  • Encephalitis
  • Hemolytic anemia
  • Renal dysfunction
  • Gastrointestinal complaints
  • Skin disorders
  • Nonspecific myalgias, arthralgias, or polyarthropathies
  • Septic arthritis

Skin disorders can include erythema multiforme, Stevens-Johnson syndrome, and toxic epidermal necrolysis.

Incubation period

The incubation period is generally between 1 to 4 weeks; however, shorter and longer durations can occur.