Overview

Croup is a respiratory disease that can affect children, but it is a rare occurrence in adults.¹ It is quite common and causes swelling in the upper part of the airways in the neck.² Croup is most commonly seen due to parainfluenzae infections and rises in frequency in the winter and autumn seasons.³ Once it takes place, it can give a range of symptoms, with the most common one being a barking cough with stridor and hoarseness.³

Croup affects younger children since they have smaller airways, but it can be a problem for babies if the swelling affects their breathing.² It is more commonly seen in 3-month-olds to 5-year-olds, with the peak being 2 years of age.²

In this article, we will tackle the link between croup and other underlying respiratory conditions and how the pre-existing conditions can influence the appearance, management and prognosis of croup.

Croup

Causes

Croup is a respiratory disease and can have multiple causes, with viral infections being the most common cause. Croup includes laryngotracheitis and laryngotracheobronchitis in its spectrum, but can have other complications that we will discuss later on. Croup origins can be classified into two:

Viral

The most common cause of viral croup is parainfluenzae viruses, with types 1 and 2 being the main agents. However, other viral agents can also cause croup, like influenza A and B, measles, adenovirus and respiratory syncytial virus.⁴

Non-Viral

Other causative agents for croup can be bacterial agents; bacterial croup is split into different groups: laryngotracheobronchitis, laryngeal diphtheria, laryngo-tracheo-bronchopneumonitis, and bacterial tracheitis. The bacterial croup is not as common as the viral one and usually occurs secondary to viral infections, meaning that the croup starts as a viral infection and then worsens after a secondary bacterial infection. The most common bacterial agents include Staphylococcus aureus, Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis.⁴ Other causes can include allergic reactions or an irritant that can induce croup-like symptoms.²

Pathophysiology

When faced with croup, swelling in the neck occurs; this is due to the infiltration of white blood cells into the larynx, trachea and large bronchi.⁴ This causes the airways to narrow down, which is already small in younger patients, and makes it harder for children to breathe, accompanied by the characteristic cough and stridor.⁴

Symptoms

There are multiple symptoms for croup, but the most common ones include:

• Barking cough with an upper respiratory infection
• Fever
• Dysphagia
• Symptoms lasting for 3 to 7 days, with the severity peaking on days 3-4⁴

If croup is suspected, its severity can be classified into 3 categories: mild, moderate and severe. This is done based on the Westley score (from 0 to 17) and it relies on 5 factors: stridor, retractions, cyanosis, consciousness levels and air entry. A mild croup is defined with a score of 2 or less, moderate croup is defined with a score between 3 to 5, and severe croup is between 6 and 11. If the score is higher than 12, then this indicates a potential respiratory failure. However, most cases of croup are mild (85% of cases), while severe croup is uncommon (<1%).⁴

Common underlying respiratory conditions

Asthma

Overview

Asthma is a common lung condition that affects people of all ages globally.⁵ It is due to the narrowing and inflammation in the lung airways, which causes difficulties in breathing, coughing, chest tightness and sometimes breathlessness.⁶

Connection to croup

Children who have asthma could have airways that have higher reactivity, which can cause croup symptoms to be worse, and studies show that children with recurrent croup have a higher chance of developing asthma.^7,8

Bronchiolitis

Overview

Bronchiolitis is a common chest infection that is seen in children and babies below the age of 2. It is a mild infection that is usually treated at home, but can be serious on some occasions.⁹ It is commonly caused by respiratory syncytial virus (RSV).¹⁰

Connection to croup

While croup is commonly due to parainfluenzae type 1, bronchiolitis is mostly due to RSV. Co-infections can occur and lead to worsening of symptoms.¹¹

Allergic rhinitis

Overview

Allergic rhinitis is an inflammation inside the nose due to allergens like pollen, dust or mould. It is a very common condition and causes sneezing, itching and a runny or congested nose.¹²

Connection to croup

Inflammation in the nose can cause croup episodes to worsen as the airways are more obstructed, making it harder for the child to breathe.¹³

Chronic obstructive pulmonary disease (COPD)

Overview

COPD is a rare illness to occur in children, it usually develops in middle-aged (or older) adults who smoke and gets worse over time. It may not be noticed by some, but it can lead to worsening of breathing issues over time. Some of the symptoms associated with COPD include shortness of breath, persistent cough with phlegm, recurrent chest infections and persistent wheezing.¹⁴ However, there are studies suggesting that COPD can develop in children due to genetic predisposition, such as alpha-1 antitrypsin deficiency.¹⁵

Connection to croup

Although COPD is rare in children, it can occur and lead to compromised lung function, which, as a result, causes croup severity to be worse.

Cystic fibrosis

Overview

Cystic fibrosis is a genetic illness that causes sticky mucus to build up in the lungs and digestive system. This illness causes the lungs to be more susceptible to infection and blockage in the airways. Over time, the damage to the lungs increases and may lead to them not functioning properly.¹⁶

Connection to croup

Due to the nature of this condition, children with cystic fibrosis will experience a longer and more severe form of croup due to their lung condition.¹⁶

Relationship between croup and underlying respiratory conditions

Following the sections above, croup and other underlying respiratory conditions can co-exist and lead to multiple outcomes:

Increased susceptibility

Children who have croup are seen to be more susceptible to developing asthma after the initial croup diagnosis, hence, it is important to monitor children for this aspect for at least 3 years.⁸

Exacerbation of symptoms

Having croup with another underlying condition can lead to the symptoms being worse than just having croup alone, e.g. having asthma or cystic fibrosis.

Complications

There is an increased risk of complications when having croup and other conditions together - for example, cystic fibrosis is a condition where the child is more susceptible to infections, and this can increase the risk of complications.¹⁶

Diagnosis of croup

Diagnosis of croup is done through multiple steps:

• Physical examination and checking clinical symptoms
• History of the patient and any underlying conditions
• Imaging tests like X-rays for the neck and chest
• Blood tests

Treatment of croup

Treatment of croup can be done through multiple steps, such as:

• Medications like steroids can help resolve the symptoms quickly and improve the child’s condition. Inhalers can also be used to help the child breathe better and ease the whistling sounds/stridor. If a bacterial infection is occurring, then antibiotics can be prescribed by the GP
• Hydration and rest at home
• Avoid smoking in the house or near the child, as this can make their cough worse
• Provide a calm environment for the child; crying and stress can increase breathing difficulties
• Using a humidifier for the air. However, steam treatment has conflicting views regarding its effectiveness
• Hospitalisation is required in case the symptoms get more severe and the child is not responding to initial treatment

Prevention of croup

There are multiple steps that we can take to try and prevent croup from occurring. Some of these steps include:

• Good hygiene practices: This includes frequent hand washing, sneezing/coughing into the elbow, avoiding meeting sick people or staying home if sick
• Immunisation and vaccination against influenza can help prevent croup from occurring
• In the presence of underlying conditions, treatment plans for these illnesses can help prevent croup from emerging. For example, lower the number of allergens and irritants around the child

Prognosis of croup

In most cases, the prognosis for croup in patients is excellent, with symptoms resolving within a week. However, recurrent croup or the presence of underlying conditions will require monitoring by their healthcare provider to oversee their treatment and outcome.

Summary

Croup is a common upper respiratory infection in children and babies. It is characterised by a barking cough, stridor and breathing issues. While most cases of croup are mild and self-limited, some cases can turn severe and even life-threatening, requiring hospitalisation. Sometimes, children have an underlying condition that can cause the croup symptoms to worsen and make it harder to manage, such as asthma or cystic fibrosis. It is important to understand and recognise the signs of each and provide the appropriate treatment possible for the child to improve their quality of life and health.