Segawa Syndrome (TH)

Segawa syndrome is an autosomal recessive disease that is caused by pathogenic variants in the TH gene. The condition has been identified in individuals of multiple ethnicities, but may have a higher prevalence in Caucasians. Onset of this neurologic disorder is typically within the first few years of life and presents with generalized dystonia. Other symptoms may include progressive lack of coordination, tremors, or abnormal eye movements. There is an earlier onset form of this disease that presents as infantile Parkinsonism and can include low muscle tone, tremors, delayed motor milestones, and abnormal functions of the brain. A more severe form of the disease also exists that presents in infancy and results in progressive infantile encephalopathy. Life expectancy of individuals with the more severe form of the disorder is variable but prognosis is good for patients with the less severe form. Several specific variants have been reported to be associated with a milder form of the disease.

For information about carrier frequency and residual risk, please see the residual risk table.