TGFB1 and Loeys-Dietz syndrome 4: Furthermore, TGFB2 haploinsufficiency pathologically activates the TGF-β signalling pathway [41], leading to Loeys-Dietz syndrome type 4 [42], which is characterised by arterial vasculopathy (arterial aneurysms, dissection and tortuosity), and other widespread connective tissue pathology, including hernia [43].