A Specialist's Point Of View: Cough in Children
Cough is one of the most common symptoms in children, resulting in a significant number of acute care visits to the Emergency department, paediatrician clinic or GP clinic in a year. Healthy children can have as frequent as six to eight acute respiratory infections in a year, and coughing during each episode may last up to two weeks (‘acute’ coughing). ‘Chronic’ cough, on the other hand, is defined as a daily cough lasting for four weeks or more. This definition is based upon expert consensus from international guidelines (American College of Chest Physicians (ACCP) and Thoracic Society of Australia and New Zealand (TSANZ)). The British Thoracic Society uses eight weeks of cough as its definition of chronic cough, but with the caveat that a “relentlessly progressive prolonged acute cough of more than three weeks may warrant investigation before eight weeks”.
Full evaluation, like most other medical conditions, includes a detailed and careful history from the child (if old enough), parents/caregivers and a thorough physical examination. In some cases, chest imaging like an Xray or a CT may be required. Others may require blood work for allergen sensitisation, immunodeficiencies, or genetic tests. Specialised procedures including pulmonary function tests, allergy skin testing, or endoscopy may also be useful in some patients.
CONDITIONS CAUSING COUGH
There are many causes of cough in children; the majority originate in the lungs, but there are also nonpulmonary etiologies, some proven and others controversial. Etiologies of chronic cough in children are quite different from those of adults. The list below highlights some conditions that are useful for clinicians to be aware of when treating a ‘coughing’ child.
Acute upper or lower respiratory infections eg.bronchitis are common in childhood. In countries with temperate climates, coughing from viral respiratory infections tend to occur more frequently in winter. In some children, ‘back to back’ infections can give the impression of a chronic, persistent cough.
Some viral infections cause prolonged periods of continuous cough (‘‘post-infectious’’ or “post-viral’’ cough), and some viral infections or atypical bacteria can result in a ‘‘pertussis-like’’ coughing syndrome. In these instances, the cough is often spasmodic and choking in nature, and may result in the classical ‘whoop’ or in vomiting. Organisms like Pertussis, Parapertussis, Adenovirus, Mycoplasma and Chlamydia have all been implicated. In young infants, Chlamydia, Cytomegalovirus, and Ureaplasma urealytica infections may also be involved.
Tuberculosis may cause chronic cough in children especially if there is secondary infection due to airway obstruction from protruding or perforating lymph nodes. In such cases, the symptoms may temporarily respond to broad spectrum antibiotics.
If airway infections are unusually frequent or severe in some children, or if unusual/opportunistic organisms are isolated, underlying primary immunodeficiencies such as IgG subclass deficiency and IgA deficiency, or granulocyte dysfunction syndromes need to be considered.
Though rare in the Asian population, cystic fibrosis (CF) should be considered if chronic airway infection is accompanied by failure to thrive. As more cases of CF get diagnosed in this part of the world, the actual prevalence may be higher than what had been previously estimated.
Persistent bacterial bronchitis (PBB)
In the past, many children with prolonged/ recurrent coughing were diagnosed as having asthma, and asthma therapies were over-prescribed and escalated. In the last 11/2 decades, the entity of persistent bacterial bronchitis (PBB) was realised as a common cause of wet cough in children. It is a chronic bacterial infection of the airways, which responds to oral antibiotics.
There are several theories as to why children get bacterial bronchitis. One is that frequent viral illnesses, especially in younger kids who attend childcare, cause airway injury and inflammation making it easier for bacteria to grow and cause infection. Children who have problems with tracheomalacia, are also at higher risk as the floppy walls of the trachea leads to the trapping of mucus in the airways.
The current criteria for diagnosing PBB is as follows: • Wet cough lasting at least 4 weeks • Absence of other findings to identify another cause of the cough • Resolution of the cough with at least 2 weeks of an antibiotic. Antibiotic options include: amoxicillin-clavulanic acid, and trimethoprim-sulfamethoxazole.
A chest x-ray may be done but findings are often non-specific. Pulmonary function testing in children old enough to cooperate may show airway obstruction. The recurrence rate is as high as 40%. Recurrent PBB is defined as >3 episodes of PBB per year.
Cough as an isolated symptom of asthma is rare, and the entity of ‘‘cough variant asthma’’ is controversial. As asthma itself is not clearly defined, with the lack of objective testing in the young age group, there are limitations in making the diagnosis in some children. It is possible that some of these children may have ‘‘hidden asthma’’—that is, they had ‘true asthma’ but were simply never heard to wheeze by their parents or doctor and therefore appearing to have isolated chronic cough.
In a child with persistent isolated non-specific coughing, some clues that may help the clinician think of asthma as a diagnosis include: (1) the demonstration of bronchodilator responsiveness (2) evidence of eosinophilic inflammation in the airways (3) personal or family history of atopy or (4) the cough responds rapidly to a trial of anti-asthma medications. However, there exist epidemiological studies that contradict this. There have been postulations that chronic cough differs from asthma in several aspects and may, therefore, have a different pathophysiology. There is also increasing evidence that, in some children with prolonged episodes of dry cough, there is a transient increase in cough receptor sensitivity.
Upper airway cough syndrome (UACS), formally known as ‘post-nasal drip’ is described to be one of the major causes of cough in children, accounting for up to 25% of all childhood chronic coughing in some studies. UACS includes various types of rhinosinus diseases that can induce cough, particularly allergic or non-allergic rhinitis and sinusitis. In some studies, constant inflammation and/or mechanical obstruction from rhinitis and adenoidal hypertrophy were two major causes of UACS in children.
In infants and children, reflux with or without aspiration of gastric content or food can cause chronic cough and wheezing. Both micro-aspiration and vagal reflexes elicited in the oesophagus may result in respiratory symptoms. Gastro-oesophageal reflux is common in many infants and the natural progression is improvement as the infant grows. Rare underlying causes that predispose to recurrent aspiration include a laryngeal cleft or tracheoesophageal fistula. Investigations and treatment are on a case by case basis, which may range from a conservative approach with positional changes or adjustment to milk feeds to reduce reflux, a trial of anti-reflux medications, to further investigations like endoscopy in some, to identify laryngeal/tracheal defects, erythematous/swollen vocal cords or the presence of lipid laden macrophages in bronchoalveolar fluid.
In a small population of patients, a chronic dry cough in a child who is otherwise healthy may suggest psychogenic cough. It may present as a habit ‘‘tic-like’’ cough or as a bizarre ‘‘honking’’ cough which bothers the parents more than the child. The cough typically becomes more noticeable with attention; and abates when the child is engrossed in an activity or at night when the child falls asleep. Characteristically, these children are in older childhood and teenage years, who are typically bright students, and they may have other somatic symptoms. Treatment includes distraction, or shifting the focus of attention away from the symptom, to breathing techniques/ hypnosis and family therapy. In many cases, the cough is a manifestation of underlying stress and conflict.
Vascular rings or slings may cause airway compression that manifest as chronic respiratory symptoms.
In children, a choking episode, or a sudden-onset cough with or without wheeze would warrant investigation for aspirated foreign bodies. Look out also for the sign of ‘unilateral’ wheezing on auscultation. Aspirated foreign bodies may go unrecognised for prolonged periods of time, especially if the diagnosis was missed initially.
A diagnosis of primary ciliary dyskinesia should be suspected in children with a combination of recurrent or severe ear, nose and throat infections and lower airway infections. Impaired mucociliary clearance of the airways leads to chronic respiratory symptoms including cough. Situs inversus is present in about 50%.
Cough is a common problem in childhood. Coughing in acute conditions tend to settle with time, without any specific management. Viral infections are the most prevalent cause, but other rarer disorders should be excluded whenever the cough is unusually severe and/or frequent, and when there is evidence of failure to thrive. A chronic ‘wet’ cough with purulent sputum is always a reason for concern and should not be attributed to asthma. Rarer diagnoses in children with a persistent cough include cystic fibrosis, aspirated foreign body, congenital anatomic abnormalities and primary ciliary dyskinesia.
Dr Petrina Wong
(Respiratory & Sleep)
MBBS (S’pore) | MRCPCH (UK) | FAMS (Paediatrics) | CCSH (BRPT) | RPSGT (BRPT)
Gleneagles Medical Centre
6 Napier Road, #08-14
Tel: 6256 1556
Dr Petrina Wong graduated from the National University of Singapore with a Bachelor of Medicine and Bachelor of Surgery in 2003. She obtained her postgraduate qualifications with the Royal College of Paediatrics and Child Health (UK) in 2007, and went on to attain accreditation as a Specialist in Paediatric Medicine in 2012. She is a Fellow of the Academy of Medicine, Singapore.
Dr Petrina Wong is a fully accredited Specialist in Paediatrics with the Ministry of Health in Singapore. She focuses on childhood respiratory and sleep conditions, in addition to general paediatrics.