Methods of treating patients having varicose veins, methods of identifying subjects having an increased risk of developing varicose veins, and methods of diagnosing varicose veins in a human subject, comprising detecting the presence of Piezo Type Mechanosensitive Ion Channel Component 1 (PIEZO1) predicted loss-of-function variant nucleic acid molecules and polypeptides in a biological sample from the patient or subject, are provided herein.