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Mr. C is a 32-year-old man with occasional wheezing.

Image not available.What is the differential diagnosis of wheezing? How would you frame the differential?

Wheezing and stridor are symptoms of airflow obstruction. These sounds are caused by the vibration of the walls of pathologically narrow airways. Wheezing is a musical sound produced primarily during expiration by airways of any size. Stridor is a single pitch, inspiratory sound that is produced by large airways with severe narrowing.

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Image not available.Stridor is often a sign of impending airway obstruction and should be considered an emergency.

The differential diagnosis for airway obstruction is large. It is best remembered by an anatomic approach. Stridor may be caused by severe obstruction of any proximal airway (see A through D in the differential diagnosis outline below). A more clinical approach to the differential appears in the algorithm at the end of the chapter.


  1. Nasopharynx and oropharynx

    1. Tonsillar hypertrophy

    1. Pharyngitis

    1. Peritonsillar abscess

    1. Retropharyngeal abscess

  2. Laryngopharynx and larynx

    1. Epiglottitis

    1. Paradoxical vocal cord movement (PVCM)

    1. Anaphylaxis and laryngeal edema

    1. Postnasal drip

    1. Benign and malignant tumors of the larynx and upper airway

    1. Vocal cord paralysis

  3. Trachea

    1. Tracheal stenosis

    1. Tracheomalacia

    1. Goiter

  4. Proximal airways

    1. Foreign-body aspiration

    1. Bronchitis

  5. Distal airways

    1. Asthma

    1. Chronic obstructive pulmonary disease (COPD)

    1. Pulmonary edema

    1. Pulmonary embolism

    1. Bronchiectasis

    1. Bronchiolitis

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Mr. C has been having symptoms for 1–2 years. His symptoms have always been so mild that he has never sought care. Over the last month, he has been more symptomatic with wheezing, chest tightness, and shortness of breath. His symptoms are worse with exercise and worse at night. He notes that he often goes days without symptoms.

Image not available.At this point, what is the leading hypothesis, what are the active alternatives, and is there a must not miss diagnosis? Given this differential diagnosis, what tests should be ordered?

The presence of wheezing, chest tightness, and shortness of breath are pivotal clues that place asthma at the top of the differential diagnosis. Although asthma is by far the most likely diagnosis, other diseases that could account for recurrent symptoms of airway obstruction should be considered. Allergic rhinitis can cause cough and wheezing but it would be very unusual for it to cause shortness of breath. Vocal cord dysfunction, such as PVCM, is frequently confused with asthma. COPD can also cause intermittent pulmonary symptoms. Table 28–1 lists the differential diagnosis.

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Table 28–1. Diagnostic Hypotheses for MR. C. 

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