Arachnodactyly, pectus deformities, mild joint laxity and high arched palate are also seen. Muscular underdevelopment, leading to a high incidence of hernias. Lens subluxation, angle anomaly, glaucoma, hypoplasia of dilator muscle, axial myopia and retinal detachment. The dislocation may be complete, with the lens floating free within the vitreous cavity. The axial length of the globe is increased in Marfan's patients leading to moderate to severe myopia as the most common refractive error.
Retinal detachment is more common than in the normal population.
Glaucoma may be the result of the angle anomaly or it may be associated with lens subluxation. The essential biochemical defect of Marfan's syndrome is unknown, but a single primary defect in collagen is suspected. To diagnose Marfan's syndrome, people with affected relative need features in at lest two systems. People with no family history need features in the skeletal system, two other systems, and one of the major criteria of ectopia lentis, dilation of the aortic root, or aortic dissection. Mutations on the cromossome 15 cause Marfan's syndrome but no diagnostic laboratory tests exists.