Other reasons are COPD, asthma, pneumothorax, pneumonia, pneumonary embolus..
Difficulty breathing can have lots of re asons, dyspnea is one of them. Dyspnea can happen just from time to time or can be permanent. Actually there are 4 levels of dyspnea. 1st level is when you do an effort (like when you go upstairs), 4th level is when dyspnea is permanent in other words, the patient have dyspnea even when he or she is sitting.