Brittle cornea syndrome (BCS) is a genetic disease involving the connective tissue in the eyes, ears, joints, and skin. The symptoms of BCS typically involve thinning of the protective outer layer of the eye (cornea), which may lead to tearing or rupture after minor damage to the cornea. Other eye symptoms may include nearsightedness (myopia), a blueish tint in the white part of the eyes (blue sclera), and retinal detachment. Other symptoms may include hearing loss, abnormal positioning of the hip bones (hip dysplasia), and soft skin with abnormal scarring.

There are 2 types of BCS. BCS type 1 is caused by changes (mutations) in the ZNF469 gene and BCS type 2 is caused by changes in the PRDM5 gene. BCS is inherited in an autosomal recessive manner. The diagnosis of BCS is made based on symptoms and may be confirmed through genetic testing. Management of BCS may include monitoring for vision loss, hearing loss, and the development of muscle or skeletal problems. Measures to prevent corneal rupture, such as wearing special protective glasses, may help delay vision loss. Other treatments may include corrective lenses (glasses), hearing aids, correcting hip dysplasia, and repairing retinal detachment.

Hearing loss may also occur and may be related to damage to the outer or middle ear (conductive hearing loss) and/or inner ear (sensorineural hearing loss). The hearing loss associated with BCS typically worsens over time.

People with BCS may also experience musculoskeletal symptoms, including hip dysplasia and abnormal curvature of the spine (scoliosis). Other symptoms may include low muscle tone (hypotonia) in infancy, long and slender fingers and toes (arachnodactlyly), and above-average joint flexibility. People with BCS may also experience a tightening and shortening of muscles around the joints (contractures), particularly involving the pinky (small, fifth finger).

People with BCS inherit one mutation from each of their parents. The parents, who each have one mutation, are known as carriers. Carriers of an autosomal recessive condition typically do not have any signs or symptoms (they are unaffected). When 2 carriers of an autosomal recessive condition have children, each child has a:

• 25% chance to be affected
• 50% chance to be an unaffected carrier like each parent
• 25% chance to be unaffected and not a carrier

While carriers of genetic diseases often do not have symptoms, carriers of BCS may have mild vision and musculoskeletal symptoms. Both corneal thinning and myopia have been reported in carriers. As such, a referral to an ophthalmologist is recommended for people who are known to be carriers of BCS or who may be at risk to be carriers. Screening for hip dysplasia may also be recommended.

While there is no one treatment for BCS, certain measures to protect the eye and cornea may help prevent damage to the cornea, for example, use of special protective glasses. In instances of serious scarring and/or thinning, a corneal transplant or corneal graft may be attempted. While these procedures may not fully restore vision, they may help to avoid further corneal damage. Corneal cross-linking may also be an option to treat corneal thinning. This procedure involves using certain vitamins (B2) to try to strengthen the connective tissue in the cornea. Other symptoms including nearsightedness, retinal detachment, hearing loss, and problems in the musculoskeletal system are managed similarly to people with these concerns in the general population.