Croup in children: meaning, causes, symptoms, treatment, mortality

By Cristiano Antonino On Jun 13, 2022

Croup in medicine refers to a disease of the respiratory system, also called ‘laryngotracheobronchitis’ to indicate inflammatory involvement of the larynx, trachea and bronchi

The inflammation is caused by an acute, often viral infection of the upper airways leading to swelling inside the throat that interferes with normal breathing and the classic symptoms: a ‘barking’ cough, stridor and hoarseness.

These symptoms can be of varying severity and tend to worsen during the night, partly due to decreased nocturnal levels of the anti-inflammatory hormone cortisol, which generally causes a fever to rise at night.

The condition mainly affects children (rare in adolescents and very rare in adults) and is usually effectively treated with a single dose of oral steroid medication; in some more severe cases, adrenaline is also used and the child may need to be hospitalised (rare).

At one time the main cause of croup in Italy was diphtheria (‘diphtheria croup’), now eradicated thanks to vaccination and improved hygiene and nutrition.

The English term ‘croup’ in Italian means ‘croup’ (meaning the rump of an animal) and is derived from the Anglo-Saxon term ‘kropan’ meaning ‘to scream loudly’ or ‘to shout in a hoarse voice’ (which is related to the symptoms of the disease in question).

Spread of croup

Croup is a rare condition among adults and relatively common in paediatric age, affecting about 15% of children, usually between 6 months and 6 years of age, accounting for about 5% of hospital admissions in this target population.

Croup only rarely occurs in children as young as three months and in boys up to 15 years of age, while it is very rare in adults.

Males are statistically affected twice as often as females.

Contrary to popular belief that croup increases in the autumn and winter months, there is no increase in prevalence on a seasonal basis.

Causes of croup

Croup is usually caused by a viral infection.

However, some clinicians use the term in a broader sense, including acute laryngo-tracheitis, spasmodic croup, laryngeal diphtheria, bacterial tracheitis and laryngotracheobronchitis.

The first two conditions involve a viral infection and are generally milder with respect to symptomatology, the last three are due to bacterial infections and usually present greater severity.

Viral infection, the cause of croup, leads to swelling of the larynx, trachea and bronchi[6] due to infiltration of blood leukocytes (mainly histiocytes, lymphocytes, plasma cells and neutrophils).

The swelling produces airway obstruction which, when significant, leads to increased work of breathing and the characteristic turbulent and noisy airflow known as ‘stridor’.

Viral croup

Viral croup – or acute laryngotracheitis – is caused by parainfluenza viruses, mainly types 1 and 2, in 75% of cases.

Other viral aetiologies include Influenzavirus A and B, measles, adenovirus and respiratory syncytial virus.

Spasmodic croup is caused by the same group of viruses as acute laryngotracheitis but the classic signs of infection, such as fever, sore throat and increased white blood cells, do not appear.

The treatment, and the response to it, are similar.

Bacterial croup

Bacterial croup can be divided into laryngeal diphtheria, bacterial tracheitis, laryngotracheobronchitis and laryngotracheobronchopneumonitis.

Laryngeal diphtheria is caused by Corynebacterium diphtheriae while the others are caused by a primary viral infection with a secondary bacterial development.

The most common bacteria involved are the bacilli Staphylococcus aureus and Streptococcus pneumoniae and the proteobacteria Haemophilus influenzae and Moraxella catarrhalis.

Signs and symptoms

Croup is characterised by symptoms that appear suddenly, which may include:

general malaise
barking cough;
stridor;
hoarseness;
disorientation;
cyanosis;
dyspnoea (difficulty breathing).

These symptoms worsen during the night hours.

The ‘barking’ cough is often described as similar to the call of a sea lion.

The stridor is often aggravated by agitation or crying and, if it can be heard at rest, may indicate critical airway narrowing, however, if the croup worsens, the stridor may paradoxically decrease.

Other symptoms, which may lead the patient’s parents to believe it is a common cold, are:

fever;
frothing at the mouth;
nasal congestion;
chest wall retraction.

Croup is diagnosed on a clinical basis once the differential diagnosis has ruled out the other potentially more serious causes of the symptoms, which are:

retropharyngeal abscess;
epiglottitis;
presence of a foreign body in the airway;
subglottic stenosis;
angioedema;
peritonsillar abscess;
allergic reaction;
laryngeal diphtheria;
bacterial tracheitis.

No further diagnostic tests are usually necessary: a frontal neck X-ray is not routinely performed, but if it is prescribed it may show a characteristic narrowing of the trachea, called the ‘bell tower sign’ because it resembles its shape.

The bell tower sign is suggestive of the diagnosis but is nevertheless absent in half of the cases.

Other investigations (such as blood tests and viral culture) are not recommended, as they may cause unnecessary agitation and thus worsen the, already compromised, airway patency.

Viral cultures, obtained by aspiration from the nasopharynx, can be used to confirm the exact cause, however, they are usually limited to research settings.

Bacterial infection should be considered if a person does not improve with standard treatment, at which point more in-depth investigations may be indicated.

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Classification of severity

The most commonly used system for classifying the severity of croup is the Westley score.

It is mainly used for research purposes rather than in clinical practice.

It consists of the sum of points assigned for five factors: level of consciousness, cyanosis, stridor, air entry and chest retraction.

A total score ≤ 2 indicates mild croup. The characteristic barking cough and hoarseness may be present, but there is no stridor at rest.
A total score of 3-5 is classified as moderate croup. It presents with easily heard stridor but few other signs.
A total score of 6-11 indicates severe croup. It presents with easily heard stridor but also with marked chest wall restriction.
A total score ≥ 12 indicates impending respiratory failure. The barking cough and stridor may no longer be important in this condition.

85% of children presenting to the emergency department for croup have a mild manifestation of the disease. Severe croup is rare (<1% of cases).

Therapies for croup

Children with croup are generally kept as calm as possible.

Steroids are routinely administered, with adrenaline used in more severe cases.

Children with arterial haemoglobin saturation below 92% must be given oxygen therapy, and in those with a severe form, hospitalisation for observation may be necessary.

If oxygen is required, blow-by administration (the oxygen source placed close to the child’s face) is recommended, as it causes less agitation than the use of a mask.

With treatment, less than 0.2 % of patients with the condition require endotracheal intubation.

Since croup is usually a viral disease, antibiotics are not used unless a secondary bacterial infection is suspected.

In such cases, vancomycin and cefotaxime are recommended.

In more severe cases associated with influenza A or B, antiviral neuraminidase inhibitors may be administered.

Steroids

Corticosteroids, such as dexamethasone and budesonide, have been shown to improve outcomes in children with croup complications.

Significant relief is achieved as early as six hours after administration.

Although they can be administered either orally, parenterally or by inhalation, the oral route remains the preferred one.

A single dose is usually sufficient and is generally considered very safe.

Doses of dexamethasone of 0.15, 0.3 and 0.6 mg/kg all appear to be equally effective.

Adrenalin

Moderate to severe croup can be temporarily ameliorated with nebulised adrenalin.

Adrenaline typically produces a reduction in severity within 10-30 minutes, the benefits lasting only about 2 hours.

If improvement persists after 2-4 hours following treatment without further complications, the child is usually discharged from hospital.

Prognosis

Viral croup is usually a self-limited disease and, in severe but well-treated cases, symptoms usually improve within two to three days but may last up to seven to ten days.

Complications

Complications are very rare and include bacterial tracheitis, pneumonia and pulmonary oedema.

Mortality

Severe croup, especially if not treated adequately and in the case of an immune deficient subject, can lead to death from respiratory failure and/or cardiac arrest, although this is a very rare occurrence.

Diphtheria croup can lead to death by suffocation.

Prevention

Many cases of croup have been prevented thanks to immunisation for influenza and diphtheria, and, as mentioned above, thanks to vaccination, croup from diphtheria is now rare.

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