Stickler syndrome, COL2A1 is a disorder of type II collagen. This common protein supports structures in the eyes, ears, and bony cartilage. The characteristic features of this disorder include very flexible (hyperextensible) joints, distinctive facial features, hearing loss, and severe nearsightedness with associated eye problems. Stickler syndrome, COL2A1 is a subtype of Stickler syndrome. The signs and symptoms of Stickler syndrome, COL2A1 vary widely among affected people. Characteristic facial features include a flattened bridge of the nose and underdeveloped cheekbones. Some children are born with an opening in the roof of the mouth (a cleft palate). The cleft palate may be associated with a tongue that is too large for the space formed by the small lower jaw; this combination of physical features is known as Robin sequence. Affected individuals are very nearsighted and have changes in the jelly-like substance inside the eyes (the vitreous). People with these eye problems tend to develop increased pressure in the eye (glaucoma), tearing of the eye lining (retinal detachment), and cataracts. Hearing is normal or the loss is generally mild, mostly affecting high tones. Hearing loss can involve both the middle ear and inner ear. This form of hearing loss is called mixed conductive and sensorineural hearing loss because it involves bone movement in the middle ear and sensory nerve cells in the inner ear. Young people with this form of Stickler syndrome often have extremely flexible joints. This flexibility lessens as they mature, and people with the condition can develop arthritis-like symptoms along with progressive spine problems and back pain.