FBN1 and Marfan syndrome: In the literature, only two cases of symptomatic MFS patients exhibit a FBN1 mosaic pathogenic variant.11,12 The past 20 years have completely altered the diagnosis of MFS and related disorders, first through the availability of capillary Sanger sequencers followed by that of the NGS technologies.13 With the latter applied to a capture panel, we discovered five cases of mosaicism in five probands for whom the diagnosis of MFS had already been ascertained at the clinical level.