Stickler syndrome and the vitreous phenotype: mutations in COL2A1 and COL11A1

Stickler syndrome is a dominantly inherited disorder affecting the fibrillar type II/XI collagen molecules expressed in vitreous and cartilage. Mutations have been found in COL2A1, COL11A1 and COL11A2. It has a highly variable phenotype that can include midline clefting, hearing loss, premature osteoarthritis, congenital high myopia and blindness through retinal detachment. Although the systemic phenotype is highly variable, the vitreous phenotype has been used successfully to differentiate between patients with mutations in these different genes. Mutations in COL2A1 usually result in a congenital membranous vitreous anomaly. In contrast mutations in COL11A1 result in a different vitreous phenotype where the lamellae have an irregular and beaded appearance. However, it is now apparent that a new sub-group of COL2A1 mutations is emerging that result in a different phenotype with a hypoplastic vitreous that fills the posterior chamber of the eye, and is either optically empty or has sparse irregular lamellae. Here we characterise a further 89 families with Stickler syndrome or a type II collagenopathy, and correlate the mutations with the vitreous phenotype. We have identified 57 novel mutations including missense changes in both COL2A1 and COL11A1 and have also detected two cases of complete COL2A1 gene deletions using MLPA.