http://footandanklecenteronline.com. Dr. Marc Baer Dr. Marc Baer DPM, FACFAS who is also Board Certified Foot & Ankle Surgery is an expert in nail fungus and what could happen if you don't treat nail fungus. Our Patients are frequently asking us about what could happen if toenail fungus goes untreated so we wanted to record a short video. If you leave nail fungus untreated, nothing very bad will happen.