Croup

In this article:

• What Is Croup?
• Symptoms
• When to see a doctor
• When to go to a hospital or ER
• Causes
• Risk Factors
• Complications
• Prevention
• Diagnosis
• Laboratory Findings
• Imaging studies
• References

---

What Is Croup?

Croup syndrome — a term uniting a group of infections of larynx (voice box) whose common feature is the obstruction of the central airways (stridor). Stridor is one of the key symptoms of laryngeal obstruction. This term refers to the harsh, often high-tone sound created by the rapid, turbulent flow of air through the narrowed large airways. 

Croup syndrome includes:

1. Pseudocroup (viral croup), 
2. Diphtheria, 
3. Epiglottitis, 
4. Fibrinous laryngotracheobronchitis. 

Another classification includes

1. Laryngotracheitis
2. Laryngotracheobronchitis
3. Laryngotracheobronchopneumonitis
4. Spasmodic croup 
5. Bacterial tracheitis. 

A viral infection (subglottic laryngitis) is the most common cause, but epiglottitis has the highest risk of mortality.

The disease is frequently reported in infants and young children in their first four years of life. It is most commonly diagnosed between 6 months and 5 years of age, peaking at 2 years of age. It rarely occurs in newborns and infants < 3 months of age. This may result from the protective role of the mother’s IgG antibodies. 

The disease affects about 3% of children and is 1.5 – 2 times more prevalent in boys than in girls. In the United States, visits to the emergency department due to acute subglottic laryngitis constitute up to 15% of all visits that are caused by respiratory diseases

---

Symptoms

Common symptoms of the croup:

1. Symptoms develop rapidly, usually 1-2 hours after a child had fallen to sleep, or at 2-3 am
2. Fever most of the time is high and difficult to bring down with OTC meds
3. Barky cough, sometimes causing a child to vomit
4. Difficulty swallowing
5. Stridor (high-pitch noise in the throat while breathing) and agitation 
6. A child is struggling while breathing

The symptoms of the disease appear suddenly, mostly in previously healthy children and usually at night a few hours after falling asleep. The most characteristic symptom is a dry, barking cough (“seal-like”) which is most often seen in young children. 

The child’s voice is usually clear, although it is sometimes accompanied by hoarseness and, on rare occasions, voice disappearing (aphonia). As the narrowing of the larynx continues, other symptoms appear, including stridor of variable intensity and difficulty of breathing in. 

When there is further increase in obstruction, stridor can also be heard during exhaling. Anxiety and crying make the symptoms worse, and make the stridor louder. These symptoms often disappear spontaneously after a few hours. Sometimes, they can be severe. 

Usually 1 to 2 days before the onset of laryngitis there are mild symptoms such as serous discharge from the nose, mildly elevated body temperature (rarely fever), sore throat, anxiety, a loss of appetite and/or malaise. In severe cases, the body temperature can be elevated and this is accompanied by anxiety, rapid breathing, shortness of breath and dyspnea. 

Increased work of the accessory respiratory muscles (supra- and subclavicular, intercostal, abdominal muscles and diaphragm) is also common. The nasal flaring intensifies. Suprasternal and chest wall retractions can be present. 

When to see a doctor

It is important that you call for an appointment if your baby is developing croup symptoms, even if you think they are mild. Why? Rapid worsening on day 2-3 may lead to severe condition, and you need to know how to manage it. 

Croup is caused by viruses which are very contagious, so if you know croup is going on in a daycare, or you had a contact with another family that now has croup – be on watch out and don’t delay the visit to a pediatric clinic. Good guidance may help you prevent an emergency visit and safely manage your child at home without panic (which is common with croup!).

When to go to a hospital or ER

You know your child best, and usually parents know well when they become uncomfortable managing a baby or a child at home. Parents with their first child are more likely to go to the ER if baby has a croup, while multiple children make parents more likely not to panic and try to get rid of croup at home. Certain signs are an acute emergency – call 911: 

1. High fever with signs of systemic toxicity 
2. Stridor – a high-pitch noise with breathing
3. Baby develops signs of dehydration – cracked lips, no visible saliva, crying without tears, does not drink liquids and does not pee (dry diper)
4. Anxiety with inconsolable cry due to inability to breathe
5. Agitation or confusion, limp unresponsive child
6. Cyanotic or pale skin (around nose and mouth)
7. Apnea – absence of breathing
8. Loss of consciousness 
9. Febrile seizures – it happens when the very high temperature suddenly goes down

Don’t be surprised if croup resolves as soon as you get into a car – cold air and distraction often works miracles! You might want to observe the child an go home instead of driving to ER – usually acute croup does not come back even if the illness continues. Call your pediatrician for a visit tomorrow, and sleep close to your child.

---

Causes

The anatomical and pathophysiological specificity of the larynx in early childhood make this group more predisposed to acute subglottic laryngitis. The main consequence of the inflammatory reaction within the larynx is inspiratory airflow disturbance with varying degrees of severity.

Acute laryngeal obstruction in the course of a  viral infection can also be caused by RSV, influenza viruses, rhinoviruses, adenoviruses, enteroviruses, coronaviruses, bocaviruses and metapneumoviruses. In unvaccinated children, the condition can be observed in measles (usually with severe obstruction). 

Herpes simplex virus has also been associated with a severe course of the disease. Less commonly, acute laryngeal obstruction can also be observed in other bacterial respiratory infections such as epiglottitis, diphtheria and fibrinous laryngotracheobronchitis.

---

Risk Factors

The disease occurs mainly in children between 6 months and 5 years of age. Some children tend to relapse.

The predisposing factors for acute subglottic laryngitis in children are:

• the shape and size of the larynx (which is genetic), 
• a tendency for submucosal swelling (especially in the subglottic region), 
• airway hyperreactivity.

---

Complications

Severe croup may cause the child to be admitted to the intensive care (ICU). The care might require emergency intubation or tracheostomy, breathing support and intravenous medications. That, in turn, may cause additional complications.

In some children (mainly boys), subglottic laryngitis is a recurrent disease. Symptoms recur during respiratory infections. This trend decreases over time.

Epidemiologically, a relationship was found which confirmed a higher risk of bronchial asthma after the occurrence of acute subglottic laryngitis. Boys with croup had a higher risk for asthma, as well as those living in cities compared to those living in the countryside.

---

Prevention

The only way to prevent croup is to avoid infection, which is almost impossible. Most children get all respiratory viruses until they are 5. It is actually healthy, as immune system learns about the viruses early, develops protective antibodies and normal responses to the bacteria and viruses.

Still, it is important to follow good hygiene to prevent the spread of the viruses in the community: 

• good hand washing 
• wearing of the mask when you have symptoms 
• staying with your child at home until symptoms resolve, or doctor allows child back to daycare or school.

---

Diagnosis

The diagnosis is clinical. It is important to tell your doctor if you know of sick contacts, and if anyone else in the family is sick. 

Studies showed that the mild form of the disease affects 85% of children, while severe symptoms are reported in less than 1%. As a consequence, the majority of children can be treated on an outpatient basis. In 60% of children, laryngeal obstruction subsides within 48 hours. In over 75% of patients, the obstruction subsides within 72 hours. Only a few cases have been reported where children had symptoms persisting for a week.

The doctor will assess the child or a baby and decide if the symptoms can be treated at home or you need to stay in the hospital:

1. General condition — the most important exponent of severity. 
2. The important indicators are the child’s activity and the ability to take in food and fluids; — the degree of respiratory problems (the severity of stridor, the presence of chest retractions, presence of paradoxical breathing, and auscultatory symptoms)
3. Other  — skin colour changes (cyanosis or pallor of the skin), gas exchange disturbances (SpO2, blood gases).

---

Laboratory Findings

Further laboratory studies and imaging are not required in typical cases. They are justified only in cases where another diagnosis is suspected. Blood tests may show an increase in some inflammatory markers such as ESR. Lymphocytosis in a peripheral blood smear may also be present. An increased CRP has been observed in very rare cases of acute subglottic laryngitis in adults. 

Although leukocyte count and ESR are often increased, blood sampling with blood culture should also be discouraged to avoid increasing the child’s anxiety and should be delayed until the airway is secure.

A swab for viruses (Flu, RSV, COVID-19) will show which infection caused croup if there is a doubt.

---

Imaging studies

Lateral X-ray of the larynx may be helpful. It shows a swollen, enlarged epiglottis (the thumb sign). It is important to note that sometimes, the image can be normal. There are no abnormalities observed in the subglottic area.

---

References

Croup. Johnson DW.BMJ Clin Evid. 2014 Sep 29;2014:0321.PMID: 25263284 Free PMC article. Review.

Croup. Sizar O, Carr B.2021 Jul 26. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan–.PMID: 28613724 Free Books & Documents. Review.

Croup: Diagnosis and Management. Smith DK, McDermott AJ, Sullivan JF.Am Fam Physician. 2018 May 1;97(9):575-580.PMID: 29763253 Free article.

Croup in children. Bjornson CL, Johnson DW.CMAJ. 2013 Oct 15;185(15):1317-23. doi: 10.1503/cmaj.121645. Epub 2013 Aug 12.PMID: 23939212 Free PMC article.