FBN1 and Marfan syndrome: Altogether, only 17 genes were primarily identified in relation to cervical insufficiency, with six being syndromic, i.e. COL1A1 and COL3A1 causing EDS; FBN1 causing Marfan syndrome; ZMPSTE24 and LMNA causing restrictive dermopathy; and MATR3 causing myopathy.