Karen is a 55 year old medical secretary who has been referred to cardiology for suspected angina over the last 2 months and is also complaining of difficulty swallowing. Initially she was suspected to have reflux and a trial of proton pump inhibitor has not helped. She has no weight loss, abdominal pain or vomiting. Past medical history includes Psoriasis and Migraine. After further tests a ‘corkscrew oesophagus’ is described on barium swallow.
What is the most likely diagnosis?