Objective: The aim of this abstract is to report a unique case of DAT positive Parkinson’s disease with a mutable Huntington’s gene.

Background: Huntington’s disease is a dominantly inherited hyperkinetic neurodegenerative disorder with CAG repeat expansion in the HTT gene, encoding a polyglutamate tract in the N-terminal part of the Huntingtin protein. 10% of the cases appear to be de novo. Intermediate alleles have 27-35 CAG repeats. Mutable normal allele is usually not associated with clinical symptoms of HD, but demonstrates meiotic instability. Mutable HD has been reported associated with behavioral changes with normal cognition and motor exam. Also, reports of late onset HD with mutable CAG repeats, and clinical HD has been reported in successive generation of patients with mutable HD. Parkinson’s disease is mostly a sporadic hypokinetic movement disorder with dopamine depletion primarily in the neurons of the substantial nigra; 15% of the cases are inherited.

Methods: We report a case of a 57 year old WF diagnosed with PD. Patient first noticed stiffness and was diagnosed with R tennis elbow in the mid 1990s. At age 47, she had masked facies, cogwheeling in the right upper extremity, micrographia, shuffling gait and decreased right arm swing. She did not exhibit tremor. Currently, she is on carbidopa/levodopa 25/100 every 2-3 hours. Interestingly, patient reported that she had a maternal grandfather who died of HD with onset in his mid 50s, a maternal aunt had symptoms of HD in her mid 50s , but patient’s mother had no signs of HD.

Results: Genetic testing was pursued. The direct testing for the HD mutation was performed by PCR amplification of genomic DNA followed by high resolution electrophoresis to determine the number of CAG repeats. The analysis identified one mutable normal allele with 29 CAG repeats and one normal allele with 22 CAG repeats. PARKIN gene testing was noted to be negative. DAT scan revealed markedly decreased radiotracer uptake L>R putamen compatible with the patients history. No additional family members have been identified with either disease.

Conclusions: This is an unusual patient with two paradoxical neurodegenerative diseases. Clinically, she is being treated for Parkinson’s symptoms with close clinical monitoring for any manifestations of Huntington’s disease. (Video to be shown). Her family is being monitored.

References: 1. Peter K.Panegyres, Judy G.S Goh, The neurology and natural history of patients with indeterminate CAG repeat length mutations of the Huntington disease gene. Journal of Neurological Sciences 2010. 2. Annie Killoran, Kevin M Biglan, et al.Characterization of the Huntington intermediate CAG repeat expansion phenotype in PHAROS. AAN 2013.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/a-unique-case-of-dat-positive-parkinsons-disease-along-with-a-mutable-huntingtons-gene/