Cough variant asthma (CVA) is a type of asthma where the only symptom is a dry cough. People with other forms of asthma have a cough that produces mucus. However, the cough in CVA is usually unproductive.
When untreated, CVA can turn into classic asthma with wheezing and shortness of breath. But CVA may be hard to diagnose. This is because a chronic dry cough is a symptom of many other conditions. Talk to your doctor if you or your child have a cough that lasts more than 4 to 8 weeks.
What are symptoms of cough variant asthma?
CVA does not show many typical signs of asthma, such as wheezing. A dry, non-productive cough is the only distinctive symptom. The cough is also chronic, meaning it lasts more than 8 weeks for adults or 4 weeks for children.1
A chronic cough can be a sign of many different conditions. Some features of the cough that indicate the involvement of asthma include:2
- Interruptions in your sleep because of coughing
- Worsening of your cough after exercise
- Worsening of your cough in cold, dry weather
- Triggering of cough episodes after exposure to allergens
What causes cough variant asthma?
We do not know the cause of CVA. CVA may be a step in the progression from atopic dermatitis (eczema) to other allergic conditions, including classic asthma. This "atopic march" happens when a child’s immune system progressively identifies new foreign substances as harmful.3
This theory is based on the fact that CVA is an early sign of classic asthma. About 30 percent of people with CVA go on to develop classic asthma. CVA is also more likely than classic asthma to go away on its own.4
How is cough variant asthma diagnosed?
CVA is one of the most common causes of chronic coughing. It can be hard to diagnose since chronic cough can indicate many other conditions. For example, your doctor may suspect other possible causes, including:1,5
- Bronchiectasis
- Congestive heart failure
- Chronic rhinosinusitis
- Chronic obstructive pulmonary disease (COPD)
- Gastroesophageal reflux disease (GERD)
To identify asthma as the cause of a chronic cough, doctors will use a combination of tests. These include:1,2,6
- Spirometry to test lung function
- Bronchoprovocation challenge tests of triggers that affect lung function
- Testing mucus (sputum) for high levels of a type of white blood cells called eosinophils
- Breath test for exhaled nitric oxide
Most people with CVA do not have as sensitive airways as people with classic asthma. This means that many of these tests may not be useful to diagnose CVA. If tests are inconclusive, your doctor may try to treat your cough with typical asthma drugs. Improvement of your cough with bronchodilators is the best way to diagnose CVA.1,2,6
How is cough variant asthma treated?
Treatment for CVA is the same as for classic asthma. Mild symptoms may just need a quick-rescue inhaler. More persistent symptoms may require daily use of an inhaled corticosteroid.1
Some doctors try to treat CVA aggressively to prevent progression to classic asthma. They may prescribe a combination of asthma treatments to resolve the cough. After the cough goes away, you may still continue taking daily inhaled corticosteroids. This can help prevent the cough from returning.1