The disorder of congenital mirror movements (CMM) is characterized by early-onset, obvious mirror movements (involuntary movements of one side of the body that mirror intentional movements on the opposite side) in individuals who typically have no other clinical signs or symptoms. Although mirror movements vary in severity, most affected individuals have strong and sustained mirror movements of a lesser amplitude than the corresponding voluntary movements. Mirror movements usually persist throughout life, without deterioration or improvement, and are not usually associated with subsequent onset of additional neurologic manifestations. However, a subset of affected individuals with a heterozygous pathogenic variant in DCC may have CMM with abnormalities of the corpus callosum and concomitant cognitive and/or neuropsychiatric issues. [from GeneReviews]