Families

The disease is caused by variants in VPS16 and is characterized by involuntary postures and abnormal movements (dystonia). These movement disorder features often begin early in life (median age at onset 12 years, range 3-50 years), with involvement of the facial, cervical, truncal, and upper limb regions. The legs are more rarely affected. The dystonia may develop towards a generalized distribution, but the disease seems to be only slowly progressive. The brain structure is often normal on MR imaging, while a subset of affected persons may show signal alterations of unknown significance. The disease is inherited in an autosomal dominant fashion, i.e., a carrier has a chance of 50% to inherit the corresponding variant to the offspring. It is important to note that not all carriers will, however, manifest the disease, since the condition is characterized by reduced penetrance (i.e., only a subset of carrier individuals will develop the disease symptoms). The exact prevalence of the disease remains to be determined.