Objective: To report a case of Juvenile Parkinson’s Disease (JP) misdiagnosed as dopa-responsive dystonia (DRD) and to emphasize the importance of early genetic testing in differentiating these conditions.

Background: Early-onset Parkinson’s Disease (EOPD) is defined by parkinsonism before age 40, with genetic mutations, particularly in the PARK2 gene, often associated with earlier onset, dystonia, and a slower progression. JP, a subtype of EOPD presenting before age 21, can be confused with DRD, which also presents with dystonia particularly in the lower limbs. Both respond to levodopa, making diagnosis challenging. Genetic tests play a key role in accurate diagnosis, prognosis and treatment.

Method: A single case report

Results: We present a 48-year-old woman with a 30-year delayed diagnosis of JP due to PARK2 mutation, initially misdiagnosed with DRD. She first exhibited right greater than left tremor as a teenager followed by foot dystonia in her 20s with diurnal fluctuations. Family history included PD in her father and maternal grandmother, and EOPD in a sister. At age 38, she was diagnosed with DRD by a movement disorder neurologist and placed on levodopa with excellent response. However, at age 48 she developed dyskinesias and motor fluctuations; additionally, symptoms seemed worse in the morning, opposite the pattern for DRD. Given her family history, a reassessment of her diagnosis was warranted. Genetic testing revealed PARK2 gene mutation on chromosome 6 with a 3-exon deletion in one allele and a missense mutation on the other. Therefore, her diagnosis was changed from DRD to JP.

Conclusion: While tremors and bradykinesia are common in JP, 42% of patients report dystonia as an initial symptom. DRD also has a broad phenotypic range, including isolated focal limb dystonia, generalized dystonia, or parkinsonism, complicating differentiation. This case highlights the importance of genetic testing in young patients to distinguish JP from DRD. The incidence of misdiagnosis is unknown, though four other cases have been reported. As genetic testing has become increasingly available, it should be a standard part of the evaluation for proper diagnosis and management. Furthermore, as we move towards precision medicine, it is crucial for potential early interventions. Misdiagnosis of JP can lead to significantly different expected long-term management, quality of life, and prognosis compared to DRD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/30-year-delayed-diagnosis-of-juvenile-parkinsons-disease-in-a-patient-misdiagnosed-with-dopa-responsive-dystonia/