The type II and XI collagenopathies are a group of disorders that affect connective tissue, the tissue that supports the body's joints and organs. These disorders are caused by defects in type II or type XI collagen. Collagens are complex molecules that provide structure, strength, and elasticity (the ability to stretch) to connective tissue. Type II and type XI collagen disorders are grouped together because both types of collagen are components of the cartilage found in joints and the spinal column, the inner ear, and the jelly-like substance that fills the eyeball (the vitreous). The type II and XI collagenopathies result in similar clinical features. Genetic changes are related to the following types of collagenopathy, types II and XI. achondrogenesis, type 2 hypochondrogenesis Kniest dysplasia otospondylomegaepiphyseal dysplasia spondyloepimetaphyseal dysplasia, Strudwick type spondyloepiphyseal dysplasia congenita spondyloperipheral dysplasia Stickler syndrome Weissenbacher-Zweymüller syndrome The system for classifying collagenopathies is changing as researchers learn more about the genetic causes of these disorders. Because there is not yet a universally accepted classification scheme, a list of other names used for these conditions, found near the end of each summary, may be helpful. The clinical features of the type II and XI collagenopathies vary among the disorders, but there is considerable overlap. Common signs and symptoms include problems with bone development that can result in short stature, enlarged joints, spinal curvature, and arthritis at a young age. For some people, bone changes can be seen only on X-ray images. Problems with vision and hearing, as well as a cleft palate (an opening in the roof of the mouth) with a small lower jaw, are common. Some individuals with these disorders have distinctive facial features such as protruding eyes and a flat nasal bridge (the upper bony part of the nose).