The Expanding Phenotypic Spectrums Associated with ATP1A3 Mutation in a Family with Rapid-Onset Dystonia Parkinsonism.

Introduction: Rapid-onset dystonia parkinsonism (RDP), also referred to as Dystonia 12, is a rare autosomal dominant genetic disease characterized by abrupt onset of a rostrocaudal gradient of dystonia with prominent bulbar symptoms, and parkinsonian features, primarily bradykinesia and postural instability without tremor. The purpose of this study was to identify the genetic defect in a Chinese pedigree with familial RDP and to explore genotype-phenotype correlation.

Methods: A 3-generation Chinese Han pedigree consisting of 9 members and 3 patients with RDP, and 200 unrelated ethnically matched normal subjects were recruited in this study. Exome sequencing was performed in the proband, and Sanger sequencing was then conducted in other family members and 200 normal controls.

Results: In addition to the typical clinical manifestations of RDP, the proband and her sister presented tongue tremor which developed at the onset, and intriguingly the proband showed a "re-emergent" tongue tremor. Both the proband and her sister had a medical history of hyperthyroidism, and at the psychiatric interview they both received diagnoses of depression and anxiety. Excessive grammar errors existed in most sentences written by the proband, and this written-expression disorder occurred years before the onset of RDP. The mother of the proband presented tongue enlargement, oromandibular dystonia, and limb dystonia, which were not observed in her 2 daughters at the time of study. A missense variant, c.1838C>T (p.T613M), in the ATP1A3 gene, was identified in the 3 patients in the family and in 2 young children but was absent in family members without RDP and in the 200 normal controls.

Conclusion: These findings may broaden the phenotypic spectrums of RDP with mutations in the ATP1A3 gene, provide new insights into the diagnosis of RDP, and have implications for genetic counseling.