Allergy Asthma Respir Dis.  2016 Mar;4(2):149-153. 10.4168/aard.2016.4.2.149.

Right middle lobe syndrome caused by eosinophilic mucoid impaction in adults

  • 1Division of Pulmonary, Allergy, and Critical Care Medicine, Department of Internal Medicine, Hallym University Sacred Heart Hospital, Hallym University College of Medicine, Anyang, Korea.
  • 2Department of Radiology, Hallym University Sacred Heart Hospital, Hallym University College of Medicine, Anyang, Korea.


Right middle lobe syndrome (RMLS) is defined as a transient or recurrent, chronic collapse of the middle lobe of the right lung by certain pathologic conditions. RMLS is a relatively uncommon condition having multiple etiologies and various clinical presentations. Two patients were referred to Hallym University Sacred Heart Hospital, one for the treatment of coughing and the other for the treatment of pneumonia. A diagnosis of RMLS was identified through X-ray and computed tomography image evaluation for each condition. Bronchoscopy revealed mucus obstruction in the right middle lobe bronchus. Biopsy of the aspirated mucus showed mucus containing many eosinophils and Charcot-Leyden crystals. After removal of impacted mucus, clinical and radiological improvements were observed in both patients. Therefore, eosinophilic mucus impaction can be considered a potential cause of RMLS, irrespective of any underlying asthmatic symptoms.


Right middle lobe syndrome; Eosinophilic mucus; Chronic cough; Pneumonia

MeSH Terms

Middle Lobe Syndrome*


  • Fig. 1 (A, B) Chest X-ray shows consolidation in right middle lobe. (C) Chest computed to-mography shows soft tissue density obstructing right middle lobe bronchus.

  • Fig. 2 (A, B) Bronchoscopic examination reveals thick mucus plug with mucosal edema and focal hemorrhagic changes in right middle lobe bronchus. (C) Biopsy specimen of mucus plug shows chronic inflammation with mucus containing many eosinophils (H&E, ×400).

  • Fig. 3 (A, B) Chest X-ray shows consolidation in right middle lobe (RML). (C) Chest computed tomography shows an endobronchial lesion obstructing RML medial segmental bronchus and (D) lobar consolidation with internal low attenuated lesion in RML.

  • Fig. 4 (A) Bronchoscopic examination reveals yellowish and thick mucus plug at the right middle lobe bronchus. (B) Biopsy specimen of mucus plug shows many eosinophils and Charcot-Leyden crystals (H&E, ×400).


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