Croup
Viral respiratory infection causing barking cough and stridor in children.
Croup is a respiratory infection, typically viral in origin, that causes swelling within the trachea, obstructing normal airflow and producing a distinctive set of symptoms. The condition is most common in children between six months and five years of age, affecting approximately 15% of children at some point, and occurs slightly more often in males than females. It is most prevalent during autumn. The classic signs include a barking or brassy cough, often compared to the call of a sea lion, along with a hoarse voice and inspiratory stridor—a harsh, noisy breathing sound heard when inhaling. Fever and runny nose may also be present. Symptoms often begin or worsen at night and typically last one to two days, ranging from mild to severe. The swelling is caused by an infiltration of white blood cells into the larynx, trachea, and large bronchi, leading to airway obstruction that increases the work of breathing and generates turbulent airflow. The most common viral cause is parainfluenza virus, responsible for about 75% of cases, though influenza A and B, measles, adenovirus, and respiratory syncytial virus can also be triggers. A related form, spasmodic croup, is caused by the same viruses but lacks typical signs of infection like fever. Bacterial croup is rare and may involve organisms such as *Corynebacterium diphtheriae*, *Staphylococcus aureus*, or *Streptococcus pneumoniae*. Diagnosis is based on signs and symptoms after ruling out more severe conditions like epiglottitis or an airway foreign body. A neck X-ray may show a steeple-like narrowing of the trachea, known as the steeple sign, but this is absent in half of cases. Severity is often assessed using the Westley score, which factors in consciousness, cyanosis, stridor, air entry, and chest retractions. Most cases are mild and managed at home with supportive care, though a single dose of oral steroids is standard treatment. In severe cases, inhaled epinephrine may be used, and hospitalization is needed in one to five percent of cases. Before widespread vaccination, diphtheria was a frequent cause, often fatal; it is now rare in the Western world due to immunization. Vaccination for influenza and diphtheria can help prevent many cases.
- field
- Respiratory infection
- known_for
- Barking cough, inspiratory stridor, hoarse voice
- common_age_range
- 6 months to 5 years
- prevalence
- Affects about 15% of children
- seasonality
- Most common in autumn
- sex_prevalence
- Slightly more common in males
Lore & Background
Croup is a respiratory infection, typically viral in origin, that causes swelling within the trachea, leading to a characteristic set of symptoms. The defining features include a distinctive "barking" or brassy cough, often compared to the call of a sea lion, along with a hoarse voice and inspiratory stridor—a harsh, noisy sound heard when breathing in. These symptoms frequently worsen at night and are usually accompanied by fever and runny nose. The condition most commonly affects children between six months and five years of age, though it can rarely occur up to age fifteen, and is slightly more common in males. It is most prevalent in autumn. The swelling results from an infiltration of white blood cells—including histiocytes, lymphocytes, plasma cells, and neutrophils—into the larynx, trachea, and large bronchi, which narrows the airway and increases the work of breathing. While most cases are mild and self-limiting, lasting one to two days, severe cases can lead to critical airway narrowing, indicated by stridor heard even at rest or a decrease in stridor as obstruction worsens. Diagnosis is made by ruling out more severe causes like epiglottitis or a foreign body; a neck X-ray may show a steeple-like narrowing of the trachea, known as the steeple sign, though this is absent in half of cases. Severity is classified using the Westley score, which considers consciousness, cyanosis, stridor, air entry, and chest wall retractions, with scores ranging from 0 (mild) to 17 (severe). Historically, before widespread vaccination, diphtheria was a frequent cause and often fatal, but this is now rare in the Western world.
Reader's Guide
Croup is a relatively common condition that affects about 15% of children at some point, most often between six months and five years of age. It is usually caused by viral infections, most commonly parainfluenza virus, and is typically mild, with most cases treated at home with supportive care. Corticosteroids, such as dexamethasone, are routinely used for moderate to severe cases, and inhaled epinephrine may be used in severe cases. Hospitalization is required in one to five percent of cases. Before vaccination, croup was frequently caused by diphtheria and was often fatal; this cause is now very rare in the Western world due to the diphtheria vaccine. Many cases are preventable by immunization for influenza and diphtheria.
Did You Know?
- Croup is characterized by a barking cough often described as resembling the call of a sea lion.
- The steeple sign, a narrowing of the trachea seen on X-ray, is suggestive of croup but is absent in half of cases.
- Croup is slightly more common in males than females.
- Less than 0.2% of children with croup require endotracheal intubation.
More in Common Infections And Diseases 1-21
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