Croup is an acute infectious laryngotracheitis which occurs mostly in children less than six years of age (although the peak incidence is around two years). It is characterized by a barking cough, hoarse voice and respiratory difficulties, which are typically seen to occur at night.
Symptoms of croup
Croup usually begins as an ordinary cold with symptoms such as a runny nose, slight rise of temperature and a mild cough.
Within a week, a child with croup develops a barking cough with noisy breathing. The voice also sounds hoarse. These symptoms start up suddenly at night, and the cough is akin to a barking seal (according to some experts). Furthermore, the breathing becomes noisy and may be of a crowing character, because of difficulty in drawing in the breath. This is called inspiratory stridor and is a sign of blockage in the airway.
This respiratory obstruction is at the tracheal level, and is due to an inflammatory reaction in the tracheal mucous lining. Children naturally have a much narrower and weaker airway than adults, thus any swelling of the mucous membrane can seriously limit the airflow through the trachea. With a greater pull on the partially blocked tracheal wall, it tends to fall inwards, worsening the blockage.
As the child grows, the cartilage in the tracheal wall becomes stronger, supporting it. This is the reason why croup is much more common in very small children. The symptoms become severe at night –probably due to the cold air which further irritates and inflames the mucosal lining. They persist for five or six nights, but rarely much longer. The most difficult time is during the first couple of nights. Croup usually gets better on its own unless it is severe or complicated.
When to seek medical attention
Apart from the noise of the breathing (which increases when the child is fussing or anxious), a real difficulty in getting in enough air may occur in about 5 out of 100 croupy children. The symptoms of this dreaded complication include:
- The neck muscles stand out while the child breathes as the work of breathing increases
- Indrawing of the spaces between the ribs as the intercostal muscles work overtime to expand the chest and improve the oxygen supply
- A bluish tinge to the lips and around the mouth, or the nails, due to deficient oxygenation
- Increased speed of breathing because the breaths are too shallow to provide enough oxygen to the body
- The breathing becomes noisy even when the child is breathing out, showing that the airway is very narrow
- The child drools or cannot swallow
- The child is very restless and sweating or looks very anxious
- Sudden onset of intractable coughing
Causes of croup
Croup is caused by a viral infection such as the parainfluenza virus, or the measles virus, respiratory syncytial virus (RSV), adenoviruses or influenza virus. These are often spread among preschool children who have not yet gained immunity to the microorganisms, such as those between three months and five years of age. However, in a few cases older children can also develop croup. The peak incidence is around 24 months, and the highest number of cases occurs between October and March.
Bacterial infections (caused by staphylococci, for instance) may also cause swelling of the trachea, also known as bacterial tracheitis. Other less common causes of croup include allergies, foreign bodies stuck in the upper trachea, inhaling irritant substances or acid regurgitating into the esophagus causing irritation of the mucous membrane and the nearby trachea.
The viruses or bacteria are transmitted by touching contaminated surfaces and then one’s eyes, nose or mouth. Inhaling respiratory droplets laden with bacteria and/or viruses that are sneezed or coughed into the air is also an important mechanism of transmission.
Reviewed by: Dr Tomislav Meštrović, MD, PhD