However, the absence (or rarity) of a familial progressive cardiac conduction disease in our patients with idiopathic LBBB is not surprising, as Lenegre Disease (when related to SCN5A mutations) more frequently shows first-degree AV block and RBBB (± LAH or LPH) and only seldom LBBB [18, 20]. Here, SCN5A is linked to heart conduction disease.