Cough-Variant asthma is a less common form of asthma that is difficult to diagnose. The only symptom associated with this form is, cough. It presents as a dry and non-productive cough meaning that the cough does not rid the lungs and airways of mucus. Nocturnal asthma is a very serious form of asthma. It occurs when asthma symptoms are present at night or during your sleep cycle. It is commonly in children representing almost half of the child asthma sufferers.