Answers

Short answers

1. Stridor.

2. Asthma is characterised by cough, wheeze, and shortness of breath. A history of only one of these symptoms—for example, isolated nocturnal cough or shortness of breath—is not enough for a diagnosis.

3. The incidence is about 1:100 000/year.

Long answers
1. Wheeze
Parents and patients will often describe any respiratory sound as wheeze. Stertor, stridor (as in this case), and rattle have all been reported as wheeze in children.¹ Stridor is a loud noise heard on inspiration. Wheeze is a softer musical sound heard during expiration. The confusion becomes less likely with increasing age but is still evident across the paediatric age range, as this case shows. Eighty percent of parents of 2 year olds reported a rattling noise as wheeze, but this proportion fell to 50% in the same population of children when assessed three years later.²

This leaves the clinician with a dilemma—when is reported wheeze genuine wheeze? A simple strategy is to ask whether the noise is a whistle or a rattle. This approach has been validated in a recent study that showed that whistle and not rattle is associated with later development of asthma.²

Vocal cord dysfunction is caused by paradoxical vocal cord motion during inspiration and is often associated with anxiety disorders.³ Many cases of vocal cord dysfunction are initially diagnosed as asthma. Before definitive diagnosis, some cases have been diagnosed as fixed airway obstruction and tracheotomy has been performed. The incidence and natural history of vocal cord dysfunction in children is unknown and treatment usually consists of speech therapy. Although vocal cord dysfunction had not been previously reported in association with thyrotoxicosis, anxiety is a feature of both conditions and is likely to explain this presentation, given that the symptoms improved greatly with antithyroid treatment.

2. Evidence against asthma
Asthma is a syndrome characterised by a triad of wheeze, cough, and shortness of breath. Isolated cough in the absence of wheeze and shortness of breath greatly reduces the likelihood of a diagnosis of asthma.³ In contrast, the presence of more than one symptom makes the diagnosis increasingly probable.⁴

Once there was a trend for asthma to be considered a diagnosis of exclusion,⁵ but this led to many children with non-specific persistent respiratory symptoms, such as isolated cough, being mislabelled as having asthma.

In the present case, the original diagnosis of asthma, based on only a night time cough, was unreliable. The diagnosis of current troublesome asthma at referral, based on shortness of breath and "wheeze," was also questionable.

No test exists for asthma, and in all ages the diagnosis of this condition can only be made by good history taking.⁴ The presence of wheeze is essential but the character of reported "wheeze" must be clarified, particularly in preschool children. Asthma is a heterogeneous condition and no more so in preschool children, where at least three (pheno)types are recognised⁶:

• Transient wheeze. Wheeze during early childhood typically with no personal or family history of allergic disease or asthma. Symptoms are often moderate-severe but infrequent and only associated with an upper respiratory tract infection. This type of wheeze is sometimes known as "viral wheeze," and it tends not to respond to corticosteroid treatment.
  
• Late onset wheeze. Wheeze that develops between ages 3 and 6 that is associated with a history of atopy and parental asthma. These children wheeze irrespective of whether they have respiratory tract infection or a cold, they have "typical" asthma, and they usually respond to treatment with inhaled corticosteroids.
  
• Persistent wheeze. These children have features of the two above asthma phenotypes and seem to have "viral wheeze" in the first three years but then develop symptoms in the absence of upper respiratory tract infection between 3 and 4 years—they become "asthmatic."
  

3. Thyrotoxicosis
Thyrotoxicosis is uncommon in children, where the incidence is approximately 1:100 000/year. Symptoms can be atypical in prepubertal children (as was the case in this boy), and heat intolerance and goitre are not common.⁷

Cite this as: BMJ 2008;337:a2289