Right Middle Lobe Syndrome Clinical Presentation

Updated: May 16, 2018
  • Author: Nemr S Eid, MD, FAAP, FCCP; Chief Editor: Denise Serebrisky, MD  more...
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The most common symptoms in right middle lobe syndrome (RMLS) include the following:

  • Persistent or recurrent cough

  • Intermittent wheezing

  • Dyspnea

  • History of recurrent or chronic pneumonia (May often be a misinterpretation of the radiographic findings)

In many cases, these respiratory symptoms are refractory to normal treatment such as antibiotics, antiinflammatory medications, and bronchodilators.

At least half of the patients report a history of asthma or atopy, and one third report a family history of atopy.

Less frequently reported symptoms, which may be indicative of chronic disease with suppurative complications, include the following:

  • Hemoptysis

  • Low-grade fever

  • Fatigue

  • Weight loss

  • Chest pain



Right middle lobe syndrome is essentially a radiographic diagnosis, and physical findings widely vary.

Auscultation of the lungs may reveal a fine wheeze, rales, or diffuse rhonchi, ranging from decreased aeration and dullness to percussion in the region of the right middle lobe. The right middle lobe is anterior, best heard at the nipple. The medial segment is located medial to the nipple; the lateral segment is lateral to the nipple. Failure to listen to this area results in failure to hear the right middle lobe.

Clubbing is rarely found in patients with advanced disease.



Intra-airway origin

In children, right middle lobe syndrome is usually secondary to primary ventilation disorders. Chronic inflammation of the airways, which contributes to atelectasis of the right middle lobe, is present. A paucity of collateral ventilation is observed in children and serves to prevent reinflation.

Primary disorders of ventilation include the following:

  • Asthma

  • Chronic pneumonia or bronchitis

  • Other chronic lung diseases caused by aspiration or gastroesophageal reflux

  • Primary ciliary dyskinesia (immotile cilia syndrome)

  • Airway foreign body aspiration 

  • Endobronchial tumors

  • Mucous plugging, as from any of the above

  • Granulation tissue

Extra-airway origin

Extraluminal compression is caused by the following:

  • Cardiovascular anomalies

  • Congenital malformations such as situs inversus and other anatomical defects such as anomalous branching or abnormal diameter, length, or structure of the bronchi

  • Lymphadenopathy of peribronchial nodes

  • Tumors

  • Traction diverticula of the esophagus

Infectious etiologies

See the list below:

  • Whether the infection is a cause of the collapse or a result of airway stasis and poor clearance may not be clear.

  • Primary infectious etiology is more frequent in adults; however, one pediatric study found that 50% of children with collapsed right middle lobe had an underlying bacterial infection. [2]

  • Infectious causes also increase in frequency among immunocompromised patients.

  • Common bacterial causes in children include Streptococcus pneumoniae and Haemophilus influenzae.

  • Fungal causes include histoplasmosis, blastomycosis, and aspergillosis, which manifest as allergic bronchopulmonary aspergillosis (APBA).

  • Mycobacteria, including Mycobacterium tuberculosis, Mycobacterium avium-intracellulare, and Mycobacterium fortuitum have also been identified as causal agents.

  • Occurrence is mainly caused by extrinsic compression by hilar lymph nodes, which are commonly observed in these infections as well as in fungal infections.