Etiology of cough

The differential diagnosis of cough in children is extensive. It has been reported that up to 31% of coughs have no apparent underlying cause. 

Primary among the causes of cough are infectious etiologies of the upper and lower respiratory tract such as sinusitis, viral upper respiratory infection, bronchiolitis, and pneumonia. Aspiration from foreign bodies, dysphagia, and gastroesophageal reflux are also common in children. However, the most frequent cause of a chronic or recurrent cough in children is asthma and may be closely linked to allergic or chronic nonallergic rhinitis. 

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Habit cough as well as tic cough also may be present in children. Inhalation pneumonitis from smoke (tobacco, fire) and hydrofluorocarbons (kerosene, gasoline) are not uncommon. Heritable disorders such as cystic fibrosis, ciliary dyskinesia, and congenital malformations of the airway also should be considered. Rarer causes of cough in children include Wegener granulomatosis and connective-tissue diseases.


Laryngotracheobronchitis, better known as croup, accounts for 15% of all respiratory disease in children. This viral infection occurs most often in the fall and winter and tends to affect children younger than age 6 years, with a peak incidence at age 18 months.

Croup is caused predominantly by parainfluenza viruses, which are present in 65% of cases. The virus seeds in the nasopharynx, then spreads distally into the respiratory epithelium of the larynx and trachea. It causes diffuse edema of the airway wall and impairs vocal cord mobility, resulting in the harsh, barky or “seal-like” cough of croup. A hoarse voice is also quite common. Stridor is an emergent sign in croup, signaling severe edema and respiratory compromise. 

Croup is more common in young children because of the much smaller, more compact laryngeal anatomic structures of the airway. As children grow, the airways with greater diameter are less susceptible to the edema caused by viruses, rendering the bark of croup is less notable. 

The most important step in evaluating children with croup is to keep them calm. Crying or screaming will increase airway resistance and worsen the stridor and respiratory distress. Allow the child to remain with a caregiver and examine him or her in as “hands off” a manner as is reasonable. 

Steroids are the standard for treatment in even mild croup as edema can progress rapidly. In one study of 720 children with croup, the patients receiving steroids had more rapid resolution and less lost sleep, and their parents experienced less stress.

 Systemic dexamethasone (Decadron, Dexamethasone Intensol, Dexpak) and nebulized budesonide (Pulmicort) were found to be equally effective. However, the cost and administration burden of nebulized budesonide makes dexamethasone a more favorable choice. Dexamethasone can be given orally or by injection. Avoidance of injection is clearly the preferred approach when attempting to keep a child calm. Dosing is 0.6 mg/kg; doses up to 10 mg have been used safely.

Racemic epinephrine should be reserved for use in children who have stridor at rest or those who are in respiratory distress. A child should be observed for several hours after administration of the racemic epinephrine to ensure that symptoms do not return or worsen.8

Patients should be admitted to the hospital if their stridor is refractory to steroids or epinephrine. Doses of these medications should continue to be given to the hospitalized child until stable.


Bronchiolitis, inflammation of the lower respiratory tract, is caused by a viral pathogen. Respiratory syncytial virus (RSV) is the most common pathogen identified and is epidemic from November to February, with geographic variations.

Bronchiolitis almost universally affects children younger than age 2 years, with peak incidence occurring at age 2 months to age 6 months. The viral culprits in bronchiolitis invade the terminal bronchiolar epithelial cells, causing tissue damage and inflammation in the airways. 

Pathologically, the damage caused includes edema, mucus production, and sloughed epithelial cells, all leading to obstruction and atelectasis. In severe cases these pathologic changes can lead to cell necrosis, ciliary injury, and peribronchial lymphocytic infiltration.11

Characteristically, children with bronchiolitis wheeze due to the obstruction in their narrowed airways. The cough of bronchiolitis will produce a wheeze as well as crackles and sputum. Depending on the degree of obstruction, many children are otherwise stable and playful. 

Nevertheless, the obstruction can be life-threatening. Infants with bronchiolitis should have very close follow-up; hospitalization should be considered for young infants who were born prematurely, because of their heightened risk for apnea.

Treatment options for bronchiolitis are limited, with no proven, efficacious therapies identified despite multiple studies. Bronchodilators and steroids are frequently used to manage the condition, especially among hospitalized patients, but have limited impact due to their ineffectiveness against the bronchogenic infiltrates of bronchiolitis.10

Several studies showed some benefit with the use of a nebulized 3% hypertonic saline. This treatment improved symptoms and reduced length of hospital stay by 26%.12,13 Supportive care with hydration, suctioning of excess secretions, supplemental oxygen, and administration of antipyretics are suggested.

Prophylaxis for high-risk infants and children is recommended during the epidemic period of RSV disease. Palivizumab (Synagis) is a monoclonal antibody given by injection every 28 to 32 days. Palivizumab does not prevent disease but can inhibit replication of the respiratory syncytial virus.11 

Premature infants born at less than 35 weeks’ gestational age, infants with neuromuscular disease or congenital airway abnormalities, and children younger than age 2 years with congenital heart disease or chronic lung disease should be considered for prophylaxis.10