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What are the different causes of persistent cough and stridor in children?

Dr Jeremy Hull looks at the different types and causes of persistent cough and stridor in children

Dr Jeremy Hull looks at the different types and causes of persistent cough and stridor in children

All children will develop a cough several times a year, the vast majority being caused by viral respiratory tract infection. In a smaller proportion the cough will persist.

If it is present on a daily basis for more than three months, a cause should be sought. For this purpose, it is useful to divide the coughs into those that are dry, and those that sound productive. To some extent this is a matter of judgment, particularly as children under the age of six are unlikely to expectorate sputum even when it is present. The common causes of dry and productive persistent cough are shown below.

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Productive-sounding coughs

The most important diagnosis to consider in this group of children is cystic fibrosis.

Any child who has a daily productive-sounding cough for more than three months should be referred for investigation. If the history is otherwise unremarkable and the physical examination and chest radiograph are normal, it is reasonable to make a working diagnosis of bronchitis.

If there are any abnormalities, or treatment for bronchitis fails to cure the cough (see below), further investigation, including sweat and immune function tests and cilial biopsy, should be carried out.

Bronchitis

Although there is little to be found about it in most paediatric respiratory textbooks, bronchitis (chronic endobronchial inflammation) is the commonest cause of chronic productive-sounding cough in our paediatric clinic population.

It usually follows an acute viral respiratory tract infection. The cough fails to resolve and is probably exacerbated by further viral and bacterial infection. The bacterial infections are low grade, and limited to the airways mucosa. Repeated infection results in persistent mucus secretion, perpetuating both the cough and the risk of subsequent infection. A prolonged (six-week) course of antibiotics combined with chest physiotherapy is usually sufficient to break the cycle. Once the chest is dry, symptoms resolve.

These children have a normal physical examination and a normal chest radiograph.

Aspirated foreign body

This is most likely to cause diagnostic difficulties in pre-school children. Taking a good history is key. If the parents report an episode of choking, followed by persistent coughing for several minutes, then referral for further investigation is indicated, even if the child subsequently appears well and physical examination is normal.

Children in whom this diagnosis is missed may subsequently present with an acute complicated pneumonia, with the risk of destruction of lung tissue, or with chronic productive-sounding cough.

Dry coughs

If a dry cough is associated with polyphonic wheezing, it is most likely caused by asthma. On the other hand, asthma is rarely the cause of an isolated dry cough and other causes should be considered.

The most common of these are post-viral and post-pertussis-like coughs.

These children are otherwise well and their coughs will eventually resolve spontaneously.

If these children are treated with inhaled steroids there will be no immediate benefit, sometimes leading to an increase in the prescribed dose. If the cough subsequently improves there may then be a temptation to ascribe this to the inhaled steroid, and maintain the dose, with the consequent risk of steroid side-effects.

If a trial of inhaled steroids is used for dry cough it should be for no longer than six weeks, and no dose escalation should be used. If there is no response, seek an alternative diagnosis.

Stridor

Stridor is the name given to the noise caused by turbulent airflow in the trachea. It arises because of a narrowed tracheal lumen. It is most usually inspiratory, but can be biphasic depending on the location and severity of the narrowing. The common causes of stridor are shown in the table below.

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Stridor starting soon after birth is most likely to be laryngomalacia, and acute stridor in pre-school children is most likely to be croup.

Laryngomalacia

This is a condition that affects about 1% of all babies. It arises because the cartilage supporting the tissue above the trachea in the larynx is softer than normal, allowing the tissue to prolapse into the tracheal opening on inspiration. It is nearly always benign and its natural history is one of gradual improvement.

Occasionally, the work of breathing to overcome the upper airways obstruction is sufficient to prevent normal growth and in these infants intervention may be required.

The stridor of laryngomalacia has characteristic qualities. It starts soon after birth, but may not be present in the first few days. It is purely inspiratory.

Dr Jeremy Hull is consultant paediatrician at John Radcliffe Hospital, Oxford

This article is an extract from Practical Paediatric Problems in Primary Care, published by Oxford University Press, edited by Mr Michael Bannon and Professor Yvonne Carter.

www.oup.co.uk ISBN 978-0-19-852922

persistent cough stridor causes Child and mother being coached on inhaler technique

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