Hi there and thank you for your interest. The Philtrum is the indentation between the nose and your upper lip. It is created by the muscle that runs like a circle around your mouth. In the philtrum the muscle fibres running from left and right cross each other, which creates the indentation in the middle, and insert into your skin, which creates the strip-like elevation we call philtre columns. There are various reasons for asymmetries. You have already pointed out very common reasons for a deviated philtrum. Other reasons could be: asymmetrical thickness of muscle-fibres, asymmetrical insertion into the skin, asymmetry of teeth or bony structures.
