Croup

Also known as laryngo- Tracheo- Bronchitis, is a type of respiratory infection that is usually caused by a virus.
The infection leads to swelling inside the trachea, which interferes with normal breathing and produces the classic symptoms of "barking/brassy" cough, inspiratory stridor and a hoarse voice.
Fever and runny nose may also be present. These symptoms may be mild, moderate, or severe.
Often it starts or is worse at night and normally lasts one to two days.
Croup can be caused by a number of viruses including parainfluenza and influenza virus.
Rarely is it due to a bacterial infection.
Croup is typically diagnosed based on signs and symptoms after potentially more severe causes, such as epiglottitis or an airway foreign body, have been ruled out. Further investigations, such as blood tests, X-rays and cultures, are usually not needed.

Stridor: Inspiratory and expiratory stridor in a 13-month child with croup
Croupy cough / Barking" cough
Hoarseness
Difficult breathing which usually worsens at night. The "barking" cough is often described as resembling the call of a sea lion. .
Other symptoms include fever, coryza, and
Hoover's sign: Indrawing of the chest wall–known as .
Drooling or a very sick appearance can indicate other medical conditions, such as epiglottitis or tracheitis.

Croup is usually deemed to be due to a viral infection.
Others use the term more broadly, to include
- Acute laryngotracheitis (laryngitis and tracheitis together)
- Spasmodic croup
- Laryngeal diphtheria
- Bacterial tracheitis
- Laryngotracheobronchitis
- Laryngotracheobronchopneumonitis.
The first two conditions involve a viral infection and are generally milder with respect to symptomatology; the last four are due to bacterial infection and are usually of greater severity.

PIV
Other viral causes include influenza A and B, measles, adenovirus and respiratory syncytial virus (RSV).
Spasmodic croup is caused by the same group of viruses as acute laryngotracheitis, but lacks the usual signs of infection (such as fever, sore throat, and increased white blood cell count). Treatment, and response to treatment, are also similar.

Croup caused by a bacterial infection is rare. Bacterial croup may be divided into laryngeal diphtheria, bacterial tracheitis, laryngotracheobronchitis, and laryngotracheobronchopneumonitis. Laryngeal diphtheria is due to Corynebacterium diphtheriae while bacterial tracheitis, laryngotracheobronchitis, and laryngotracheobronchopneumonitis are usually due to a primary viral infection with secondary bacterial growth. The most common cocci implicated are Staphylococcus aureus and Streptococcus pneumoniae, while the most common bacteria are Haemophilus influenzae, and Moraxella catarrhalis.

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