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Key Features

Essentials of Diagnosis

  • Pathologic features

    • Shedding of airway epithelium

    • Edema

    • Mucus plug formation

    • Mast cell activation

    • Collagen deposition beneath the basement membrane

  • The inflammatory cell infiltrate includes eosinophils, lymphocytes, and neutrophils, especially in fatal asthma exacerbations

  • Airway inflammation contributes to

    • Airway hyperresponsiveness

    • Airflow limitation

    • Disease chronicity

  • Persistent airway inflammation can lead to airway wall remodeling and irreversible changes

General Considerations

  • Atopy is the strongest identifiable predisposing factor

  • About 40% of infants and young children who have wheezing with viral infections in the first few years of life will have continuing asthma through childhood

  • Viral infections (eg, respiratory syncytial virus [RSV], rhinovirus, parainfluenza and influenza viruses, metapneumovirus) are associated with wheezing episodes in young children

  • Acetaminophen exposure

    • May increase risk of asthma during prenatal periods, infancy, childhood, and even adulthood

    • Evidence suggests that it increases the risk for subsequent asthma exacerbations or wheeze compared to ibuprofen

  • Triggers for asthma

    • Exposure to tobacco smoke

    • Exercise

    • Cold air

    • Pollutants

    • Strong chemical odors

    • Rapid changes in barometric pressure

    • Psychological factors


  • Most common chronic disease of childhood, affecting over 7 million children in the United States

  • Up to 80% of children with asthma develop symptoms before their fifth birthday

  • Gender, race, and socioeconomic disparities in the prevalence of asthma exist

    • More boys than girls are affected in childhood

    • Higher percentage affected among black children compared to Hispanic and non-Hispanic white children

    • Children belonging to poor families are more likely to be affected

Clinical Findings

Symptoms and Signs

  • Wheezing

  • Recurrent cough

  • Shortness of breath

  • Complaints may include "chest congestion," prolonged cough, exercise intolerance, dyspnea, and recurrent bronchitis or pneumonia

  • With severe obstruction, wheezes may not be heard because of poor air movement

  • Flaring of nostrils, intercostal and suprasternal retractions, and use of accessory muscles of respiration are signs of severe obstruction

  • Cyanosis of the lips and nail beds may be seen with underlying hypoxia

  • Tachycardia and pulsus paradoxus also occur

  • Agitation and lethargy may be signs of impending respiratory failure

Differential Diagnosis

  • Viral bronchiolitis

  • Aspiration

  • Laryngotracheomalacia

  • Vascular rings

  • Airway stenosis or web

  • Enlarged lymph nodes

  • Mediastinal mass

  • Foreign body

  • Bronchopulmonary dysplasia

  • Obliterative bronchiolitis

  • Cystic fibrosis

  • Vocal cord dysfunction

  • Cardiovascular disease


Laboratory Findings

  • Bronchial hyperresponsiveness to nonspecific stimuli is a hallmark of asthma

    • Stimuli include histamine, methacholine, mannitol, exercise, and cold air

    • Mannitol bronchoprovocation is simpler and easier to administer in the office

    • Giving increasing concentrations of a bronchoconstrictive agent to induce a decrease in lung function (usually a 20% drop in forced expiratory volume in 1 second [FEV1] for histamine and methacholine and a 15% reduction for mannitol) and doing an exercise challenge are ways to determine ...

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