Researchers have identified the fifth gene linked to Joubert syndrome (JS), a rare, genetic disorder that affects the area of the brain that controls balance and coordination, and is thus characterized by ataxia (lack of muscle control), an abnormal breathing pattern called hypernea, sleep apnea, abnormal eye and tongue movements, hypotonia, and possibly, other physical malformations.

Joubert syndrome can result in developmental delay, poor physical coordination, irregular breathing, visual impairment, kidney failure and extra digits. Diverse symptoms may occur making diagnosis difficult, though patients typically feature a characteristic configuration of the brainstem and cerebellum on magnetic resonance imaging (MRI), where the abnormally developed brain stem resembles the shape of a molar tooth. The researchers' discovery of mutation in the gene (RPGRIP1L) now paves the way for definitive DNA testing that can more conclusively diagnose JS in some patients, and also identify asymptomatic carriers who might unknowingly pass the condition to their future children.

Not only will these findings aid in the diagnosis of the disease, it may also pave the way for potential therapies.