Step 1: Note the cluster: sudden severe anxiety with choking, chest tightness, breathlessness, palpitations and a sense of impending doom.
Step 2: Crucially, all systemic examination is normal, so an organic cardiorespiratory cause is excluded. This abrupt, self-limited surge of intense fear with autonomic symptoms is a panic attack, and recurrent attacks define panic disorder.
Why not the others: Depression is low mood and loss of interest over weeks, not paroxysmal choking and doom. Epilepsy is a neurological seizure disorder, not this autonomic anxiety picture with a normal exam. Asthma would show wheeze and signs on respiratory examination, which here are normal.
Ref: Arvind Arora Review of Psychiatry p.131.