Delayed Diagnoses of SGCE Myoclonus-Dystonia.

Background: Myoclonus-dystonia due to SGCE mutations (OMIM: 159900) most commonly presents during childhood with mainly upper body myoclonus, and mild dystonia affecting the neck and arms.

Case reports: Herein, we report patients misdiagnosed during childhood with Tourette syndrome and dyskinetic cerebral palsy, and, during adulthood, found to harbor SGCE frameshift mutations.

Discussion: Myoclonus-dystonia may be underdiagnosed due to phenotypic misclassification during childhood. SGCE mutations should be included in the differential diagnosis of childhood movement disorders that ostensibly manifest with tics, myoclonus, or abnormal posturing secondary to dystonia and/or spasticity.

Highlights: Due to pleiotropy, variable penetrance, broad differential, and hereditary effects of imprinting, the diagnosis of a disorder of childhood onset, myoclonus-dystonia due to SGCE mutations, may be delayed until adulthood, often compromising appropriate clinical management and genetic counseling.