Cockayne syndrome type III, also known as the mild form of Cockayne syndrome, is a rare genetic disorder that causes early (premature) aging. Unlike the more severe forms of this condition, individuals with Cockayne syndrome type III can have normal growth and development. Symptoms may include sunlight sensitivity (photosensitivity), hearing loss, eye and bone abnormalities, and changes to the brain that can be seen on imaging (brain MRIs). In general, symptoms of Cockayne syndrome type III are usually not noticeable until later in childhood.
Cockayne syndrome type III is caused by changes (mutations) in either the ERCC6 or ERCC8 gene. These genes act as instructions for the body to make proteins that are important for DNA repair. DNA damage typically occurs from exposure to the sun, toxic chemicals, or radiation. Normally, the body is able to repair this damage before it causes health issues. However, individuals with this condition cannot repair the damage fast enough, which causes cells to die off early and leads to the premature aging seen in Cockayne syndrome type III. This condition is inherited in an autosomal recessive way, which means a mutation in both copies of the gene a child has is needed to cause Cockayne syndrome type III.
Cockayne syndrome type III is considered in children who have features of premature aging that did not present until later in childhood. The diagnosis can be confirmed with a test that looks for DNA repair problems on a piece of skin (biopsy) or with genetic testing. Although there is no cure for Cockayne syndrome type III, there are options to help decrease the symptoms, including the use of strong sunscreen and avoiding sunlight. If your child has been diagnosed with Cockayne syndrome type III, talk to their doctor about all treatment options. Support groups can provide more information and connect you with other affected families.