Cough-variant asthma is a type of asthma in which cough is the dominant and sometimes only symptom. A person with cough-variant asthma experiences dry, generally nonproductive cough without wheezing or breathlessness. The cough in that situation is considered to be a wheeze equivalent. The cough in cough-variant asthma may be provoked by triggers such as cold air or viral upper respiratory tract infections. Like “typical” asthma, there is usually a significant nocturnal component. Cough-variant asthma is more common in young children, yet has been described in all age groups, from toddlers to seniors. Since a chronic or longstanding cough can be a symptom of many different illnesses, confirming a diagnosis of cough-variant asthma may be challenging and requires a certain degree of suspicion from the onset.
The chest X-ray is normal in cough-variant asthma, as are spirometry and other pulmonary-function tests. Evaluation may include undergoing bronchoprovocation testing, such as a methacholine challenge test. Some experts consider that a favorable response to a trial of appropriate asthma medicine clinches the diagnosis. Effective treatment typically requires anti-inflammatory corticosteroid medication. If there is no response to the inhaled form of corticosteroid after 8 weeks, then a course of oral (pill form) steroids is indicated, which can often yield prompt and dramatic improvement. Bronchodilators are often part of the treatment regimen, along with corticosteroids as cough-variant asthma does respond to standard therapies. Medication from the leukotriene antagonist class can also be effective. Studies indicate that up to 30% of individuals diagnosed with cough-variant asthma will, in time, go on to develop more typical asthma.
Important points about cough-variant asthma include:
- Cough-variant asthma is a subclass, or variant, of asthma.
- Although individuals with asthma can experience cough as one symptom along with wheezing and breathlessness, individuals with the cough-variant form have only cough as a symptom, usually with-out wheezing or breathlessness.
- The chest X-ray is normal.
- Pulmonary function tests are normal.
- Methacholine challenge testing is abnormal, or “positive.”
- Corticosteroids, either inhaled or in pill form, are effective treat-ments and should be part of the treatment regimen.
- The response to oral corticosteroids can be dramatic, with marked improvement in as little as 24 hours.
- A person with dry cough for three weeks or more should be evalu-ated for possible cough-variant asthma, especially if the chest X-ray and pulmonary function tests are normal.
- Other causes of chronic dry cough of three weeks’ duration or more with normal chest X-ray and spirometry include: gastroesophageal reflux (GERD), postnasal drip or discharge, and cough following a viral respiratory illness.