Asthma is a chronic lung condition that causes inflammation and narrowing of the airways, which results in difficulty breathing. Asthma generally develops in childhood and may sometimes resolve with age. Many individuals, however, continue to experience asthma or asthma-related symptoms into adulthood. Additionally, there are cases of adult-onset asthma where an individual is not diagnosed with asthma until after age 18. Asthma is known to have a strong genetic component, which means that if you have asthma, there is a chance that others in your family may have asthma as well.