Spinocerebellar ataxia type 3 with dopamine-responsive dystonia: A case report

BACKGROUND: Spinocerebellar ataxia type 3 (SCA3) is a rare neurodegenerative disease with high genetic heterogeneity. SCA3 mainly manifests as progressive cerebellar ataxia accompanied by paralysis of extraocular muscles, dysphagia, lingual fibrillation, pyramidal tract sign, and extrapyramidal system sign. However, it rarely has clinical manifestations similar to Parkinson-like symptoms, and is even rarer in patients sensitive to dopamine. We report a patient initially diagnosed with dopamine-responsive dystonia who was ultimately diagnosed with SCA3 by genetic testing, which was completely different from the initial diagnosis. CASE SUMMARY: A 40-year-old Chinese woman was admitted to hospital due to severe inflexibility. At the beginning of the disease, she presented with anxiety and sleep disorder. At the later stage, she presented with gait disorder, which was similar to Parkinson's disease. Her medical history was unremarkable, but her mother, grandmother, and uncle all had similar illnesses and died due to inability to take care of themselves and related complications. Laboratory and imaging examinations showed no abnormalities, but electromyography and electroencephalography revealed delayed somatosensory evoked potentials and slow background rhythm, respectively. Her symptoms fluctuated during the daytime, and we initially diagnosed her with dopamine-responsive dystonia. After treatment with low-dose levodopa, the patient’s symptoms were significantly improved, but the final genetic diagnosis was SCA3. CONCLUSION: SCA3 has various clinical phenotypes and needs to be differentiated from Parkinson's syndrome and dopamine-responsive dystonia.