Dickson, Dennis W

AbstractBackgroundFamilies of Dutch‐German‐Russian Mennonite descent with multi‐incident parkinsonism have been identified as harboring a pathogenic DNAJC13 p.N855S mutation and are awaiting clinical and pathophysiological characterization.MethodsFamily members were examined clinically longitudinally, and 5 underwent dopaminergic PET imaging. Four family members came to autopsy.ResultsOf the 16 symptomatic DNAJC13 mutation carriers, 12 had clinically definite, 3 probable, and 1 possible Parkinson's disease (PD). Symptoms included bradykinesia, tremor, rigidity, and postural instability, with a mean onset of 63 years (range, 40‐85) and slow progression. Eight of ten subjects who required treatment had a good levodopa response; motor complications and nonmotor symptoms were observed. Dopaminergic PET imaging revealed rostrocaudal striatal deficits typical for idiopathic PD in established disease and subtle abnormalities in incipient disease. Pathological examinations revealed Lewy body pathology.ConclusionPD associated with a DNAJC13 p.N855S mutation presents as late‐onset, often slowly progressive, usually dopamine‐responsive typical PD. © 2014 International Parkinson and Movement Disorder Society

ABSTRACTBackgroundWe have reported that intermediate repeat lengths of the C9ORF72 repeat are a risk factor for Parkinson's disease (PD) in a clinically diagnosed data set. Because 10% to 25% of clinically diagnosed PD have different diagnoses upon autopsy, we hypothesized that this may reflect phenotypic heterogeneity or concomitant pathology of other neurodegenerative disorders.MethodsWe screened 488 autopsy‐confirmed PD cases for expansion haplotype tag rs3849942T. In 196 identified haplotype carriers, the C9ORF72 repeat was genotyped using the repeat‐primed polymerase chain reaction assay.ResultsNo larger (intermediate or expanded) repeats were found in these autopsy‐confirmed PD samples. This absence of larger repeats is significantly different from the frequency in clinically diagnosed datasets (P = 0.002).ConclusionsOur results suggest that expanded or intermediate C9ORF72 repeats in clinically diagnosed PD or parkinsonism might be an indication of heterogeneity in clinically diagnosed PD cases. Further studies are needed to elucidate the potential contribution of the C9ORF72 repeat to autopsy‐confirmed PD. © 2014 International Parkinson and Movement Disorder Society

ABSTRACTBackgroundVariants within the leucine‐rich repeat kinase 2 gene are recognized as the most frequent genetic cause of Parkinson's disease. Leucine‐rich repeat kinase 2 variation related to disease susceptibility displays many features that reflect the nature of complex, late‐onset sporadic disorders like Parkinson's disease.MethodsThe Genetic Epidemiology of Parkinson's Disease Consortium recently performed the largest genetic association study for variants in the leucine‐rich repeat kinase 2 gene across 23 different sites in 15 countries.ResultsHerein, we detail the allele frequencies for the novel risk factors (p.A419V and p.M1646T) and the protective haplotype (p.N551K‐R1398H‐K1423K) nominated in the original publication. Simple population allele frequencies not only can provide insight into the clinical relevance of specific variants but also can help genetically define patient groups.ConclusionsEstablishing individual patient‐based genomic susceptibility profiles that incorporate both risk factors and protective factors will determine future diagnostic and treatment strategies. © 2013 International Parkinson and Movement Disorder Society