Stickler syndrome is a group of hereditary conditions characterized by a distinctive facial appearance, eye abnormalities, hearing loss, and joint problems. Genetic changes are related to the following types of Stickler syndrome. Stickler syndrome, COL11A1 Stickler syndrome, COL11A2 Stickler syndrome, COL2A1 Whether there are two or three types of Stickler syndrome is controversial. Each type is presented here according to the gene involved. The classification of these conditions is changing as researchers learn more about the genetic causes. Stickler syndrome is a subtype of collagenopathy, types II and XI. Individuals with Stickler syndrome experience a range of signs and symptoms. Some people have almost no signs and symptoms; others have all of the features described below. In addition, each feature of this syndrome may vary from subtle to severe. A characteristic feature of Stickler syndrome is a somewhat flattened facial appearance. This is caused by underdeveloped bones in the middle of the face, including the cheekbones and the bridge of the nose. A particular group of physical features, called Robin sequence, is common in children with Stickler syndrome. Robin sequence includes a U-shaped cleft palate (an opening in the roof of the mouth) with a tongue that is too large for the space formed by the small lower jaw. Children with a cleft palate are also prone to frequent ear infections and swallowing difficulties. Many people with Stickler syndrome are very nearsighted (described as having high myopia) because of the shape of the eye. People with eye involvement are prone to increased pressure within the eye (glaucoma) and tearing of the lining of the eye (retinal detachment). The jelly-like substance within the eye (the vitreous) has a distinctive appearance in the types of Stickler syndrome associated with the COL2A1 and COL11A1 genes. The type of Stickler syndrome associated with the COL11A2 gene does not affect the eye. Another sign of Stickler syndrome is mild to severe hearing loss that, for some people, may be progressive. The joints of affected children and young adults may be very flexible (hypermobile). Arthritis often appears at an early age and worsens as a person gets older.