Mr. C is a 32-year-old man with occasional wheezing.
|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.
|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.
Nasopharynx and oropharynx
Laryngopharynx and larynx
Paradoxical vocal cord movement (PVCM)
Anaphylaxis and laryngeal edema
Benign and malignant tumors of the larynx and upper airway
Vocal cord paralysis
Chronic obstructive pulmonary disease (COPD)
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.
|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.
Table 28–1. Diagnostic Hypotheses for MR. C.
| Save Table
Table 28–1. Diagnostic Hypotheses for MR. C.
|Diagnostic Hypotheses||Clinical Clues||Important Tests|
|Asthma||Episodic and reversible airflow obstruction|
Response to treatment
|Allergic rhinitis||Rhinitis with seasonal variation||Response to treatment|
|Vocal cord dysfunction||Voice pathology accompanies airflow obstruction||Abnormal vocal cord movement visualized|
|Active Alternative—Must Not Miss|
|COPD||Presence of smoking history||PFTs|
On further history, Mr. C reports that he had asthma as a child and was treated for years with theophylline. He was without symptoms until he moved 2 years ago.
He reports that his symptoms are worst when he has a cold, when he jogs, and when he is around dogs or cats. His most common symptoms are chest tightness and dyspnea. Only when his symptoms are at their worst does he hear wheezing. He has never smoked cigarettes.
On physical exam he appears well. His vital signs are BP, 120/76 mm Hg; RR, 14 breaths per minute; pulse, 72 bpm; temperature, 36.9°C. His lung exam is normal without wheezes or prolonged expiratory phase. His peak flow is 550 L/min (87% of predicted).
|Is the clinical information sufficient to make a diagnosis? If not, what other information do you need?|
Leading Hypothesis: Asthma
Asthma commonly presents as recurrent episodes of dyspnea, often with chest tightness, cough, and wheezing. Patients usually report stereotypical triggers (eg, allergens, cold weather, exercise) and rapid response to β-agonist inhalers. Asthma is so common that most patients have diagnosed themselves prior to presentation.
Definition: The NIH/NHLBI definition of asthma is “A chronic inflammatory disease of the airways in which many cells and cellular elements play a role.” “In susceptible individuals, this inflammation causes recurrent episodes of wheezing, breathlessness, chest tightness, and cough, particularly at night and/or in the early morning. These episodes are usually associated with widespread but variable airflow limitation that is often reversible either spontaneously or with treatment.”
Asthma is recurrent and intermittent. Patients will have periods with no or only mild symptoms unless severe disease develops when patients have persistent symptoms.
Asthma usually presents during childhood but presentation as an adult is not uncommon.
People with asthma have fluctuation of airway function.
Airway function is most commonly mea sured by peak expiratory flow (PEF).
Values are generally lowest in the morning and highest at mid-day.
PEF will vary by more than 20% in asthmatic patients over the course of the day.
Identifying exacerbating factors and timing of symptoms is important. It aids in the diagnosis of asthma (exacerbating factors are stereotypical) and in treatment (if the factors are reversible).
Asthma frequently worsens at night (probably related to decreased mucociliary clearance, airway cooling, and low levels of endogenous catecholamines).
Asthma frequently worsens with exercise (probably related to airway cooling and drying).
Viral infections are a common cause of asthma exacerbations.
Occupational agents may cause or exacerbate asthma by a number of mechanisms:
Corrosive agents (ammonia)
Pharmacologic agents (organophosphates)
Reflex bronchoconstriction (ozone)
Asthma should be in the differential diagnosis of any patient with intermittent respiratory symptoms.
Classification: The present classification scheme for asthma helps focus attention on the severity of ...
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