1 , ▁a ▁major ▁constitu ent ▁of ▁ext rac ell ular ▁micro f ibr ils ▁which ▁form ▁connect ive ▁t issues . ▁ ▁Over ▁ 1 , 0 0 0 ▁different ▁mut ations ▁in ▁FB N 1 ▁have ▁been ▁found ▁to ▁result ▁in ▁ab normal ▁function ▁of ▁f ibr ill in , ▁which ▁consequ ently ▁rel ates ▁to ▁connect ive ▁t issues ▁el ong ating ▁progress ively ▁and ▁weak ening . ▁Because ▁these ▁fib ers ▁are ▁found ▁in ▁t issues ▁throughout ▁the ▁body , ▁mut ations ▁in ▁this ▁gene ▁can ▁have ▁a ▁w ides p read ▁effect ▁on ▁certain ▁systems , ▁including ▁the ▁ske let al , ▁card i ov asc ular , ▁and ▁nerv ous ▁system , ▁as ▁well ▁as ▁the ▁eyes ▁and ▁l ungs . ▁ ▁Without ▁medical ▁inter vention , ▁pro gn osis ▁of ▁Mar fan ▁synd rome ▁can ▁range ▁from ▁moder ate ▁to ▁life - th re aten ing , ▁with ▁ 9 0 % ▁of ▁known ▁causes ▁of ▁death ▁in ▁diagn osed ▁patients ▁rel ating ▁to ▁card i ov asc ular ▁comp lications ▁and ▁con gest ive ▁card iac ▁failure . ▁ ▁Other ▁characteristics ▁of ▁M FS ▁include ▁an ▁increased ▁arm ▁span ▁and ▁decre ased ▁upper ▁to ▁lower ▁body ▁ratio . ▁ ▁" M ini - mus cle " ▁alle le ▁ ▁A ▁gene ▁recently ▁discovered ▁in ▁labor atory ▁house ▁m ice , ▁term ed ▁" min i - mus cle ", ▁causes , ▁when ▁mut ated , ▁a ▁ 5 0 % ▁reduction ▁in ▁h ind lim