tokens: We found that ( 1 ) the number of apparently de novo events is much higher than the classically admitted number ( around 50 % of patients and not 25 % as expected for FBN1 ) and ( 2 ) around 5 % of the FBN1 disease - causing variants were not actually de novo as anticipated , but inherited in a context of somatogonadal mosaicisms revealed in parents from three families .