BRAF and familial atrioventricular septal defect: Between 57 and 75% of patients with ECD carry the BRAFV600E mutation, an activating mutation of the proto-oncogene BRAF. More than 50 patients worldwide with BRAF mutations and severe multisystem refractory ECD (sometimes accompanied by Langerhans cell histiocytosis, LCH) have received vemurafenib.