Stickler syndrome

The syndrome is thought to arise from a mutation of several collagen genes during fetal development. It is a sex independent autosomal dominant trait meaning a person with the syndrome has a 50% chance of passing it on to each child.
There are three variants of Stickler syndrome, each associates with a collagen biosynthesis gene. Stickler syndrome is an autosomal dominant condition, meaning only one parent needs to have an abnormal gene for the child to inherit the disease.

A person with Stickler syndrome has a 50% chance for each pregnancy of passing this mutation on to the child. For some people, the Stickler syndrome gene mutation is inherited from a parent. 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 the Pierre 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 calciam. 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 (see hearing loss with craniofacial syndromes). 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. Learning difficulties can also occur because of hearing and sight impairments.

Mutations in the COL11A1, COL11A2 and COL2A1 genes cause Stickler syndrome. These genes are involved in the production of type II and type XI collagen. Collagens are complex molecules that provide structure and strength to connective tissue (the tissue that supports the body's joints and organs). Mutations in any of these genes disrupt the production, processing, or assembly of type II or type XI collagen.

Defective collagen molecules or reduced amounts of collagen affect the development of bones and other connective tissues, leading to the characteristic features of Stickler syndrome. Other, as yet unknown, genes may also cause Stickler syndrome because not all individuals with the condition have mutations in one of the three identified genes.