FBN1 and Weill-Marchesani syndrome: It remains unclear why the vast majority of known mutations throughout fibrillin-1 cause Marfan syndrome, but that certain mutations in TB5 specifically cause WMS, AD and GD [16] and in the RGD-containing TB4 cause Stiff Skin syndrome, a congenital scleroderma with thickened skin and limited joint mobility [35].