Author(s): Leslie S Libow
Background/Objectives: The two major ''diseases of tremor'' are Parkinson's Disease (PD) and Essential Tremor (ET). There is disagreement as to any linkage of these two entities. This report focuses on ''elderly identical twins'' wherein one twin manifests PD and the other one manifests ET.
Design: Blood samples from each twin were studied in our medical school's genetics laboratory. Pleasingly the genetic identity of the sisters was 99.9%.
Setting: One twin resided for many years at a teaching nursing home because of her disabling PD. The other twin lived independently in an apartment a few moments from the nursing home and visited her sister daily. Ultimately, the healthier twin, for convenience, also moved within a room at the teaching nursing home.
Participants: These identical twins were born in England. Their migration to America brought them to New York City and ultimately to the more disabled twin came under our care at our ''teaching nursing home.'' Intervention: The ill twin was under the continual care of an associate professor of neurology at the Mount Sinai School of Medicine. The healthier community residing twin was evaluated by the ''Professor of Medicine/Geriatrics'' of our teaching nursing home. Traditional therapy for PD was administered. The twin with PD experienced some deterioration.
Measurements: Traditional neurological evaluations were done repeatedly and blood samples from both sisters were analyzed for their genetics.
Results: The genetic testing showed 99.9% concordance of the twins. The twin with PD continued to experience neurological deterioration. The healthier twin, after several years in her own apartment near the teaching nursing home, found it necessary to reside permanently at the teaching nursing home. She never demonstrated PD.
Conclusion: The simultaneous appearance of PD and ET in genetically proven identical twins strongly suggests a biologic linkage of these two diseases of tremor (PD and ET).
