Links between impulsive compulsive behaviors in treated Parkinson’s disease, behavioral addictions and substance abuse have been postulated, but no direct comparisons have been carried out so far. We directly compared patients with Parkinson’s disease with and without impulsive compulsive behaviors with illicit drug abusers, pathological gamblers and age-matched healthy controls using the beads task, a test of reflection impulsivity and a working memory task. We found that all patients with Parkinson’s disease made more impulsive and irrational choices than the control group. Parkinson’s disease patients who had an impulsive compulsive behavior showed similar behavior to illicit substance abusers whereas patients without impulsive compulsive behaviors more closely resembled pathological gamblers. In contrast we found no difference in working memory performance within the Parkinson’s disease groups. However Parkinson’s disease patients without impulsive compulsive behaviors remembered distractors significantly less than all other patients during working memory tests. We were able to correctly classify 96% of the Parkinson’s disease patients with respect to whether or not they had an impulsive compulsive behavior by analyzing 3 trials of the 80/20 loss condition of the beads task with a negative prediction value of 92.3% and we propose that this task may prove to be a powerful screening tool to detect an impulsive compulsive behavior in Parkinson’s disease. Our results also suggest that intact cortical processing and less distractibility in Parkinson’s disease patients without impulsive compulsive behaviors may protect them from developing behavioral addictions.

See Gandhi and Plun-Favreau (doi:) for a scientific commentary on this article.Heterozygous mutations in recessive Parkinson’s disease genes have been postulated to increase disease risk. Puschmann et al. report a genetic association between heterozygous PINK1 p.G411S and Parkinson’s disease. They provide structural and functional explanations for a partial dominant-negative effect of the mutant protein, which impairs wild-type PINK1 activity through hetero-dimerization.

Overall, our findings suggest that MAPT p.A152T is a rare low penetrance variant likely associated with DLB that may be influenced by coexisting LBD and AD pathology. Given the rare nature of the variant, further studies with greater sample size are warranted and will help to fully explain the role of p.A152T in the pathogenesis of the synucleinopathies.

Aims To examine a syndrome of chronic manganism that occurs in drug addicts in Eastern Europe who use intravenous methcathinone (ephedrone) contaminated with potassium permanganate. The basal ganglia, especially the globus pallidus and the putamen, are damaged irreversibly in many cases. Routine neuropsychological assessment has revealed no cognitive deficits despite widespread abnormalities on brain imaging studies and severe extrapyramidal motor handicap on clinical examination. Design Case control study. Setting Ephedrone patients and patients with opioid dependence were recruited from Lviv, Ukraine. Participants We tested 15 patients with ephedrone induced toxicity, 13 opiate dependent patients, who were receiving opioid replacement therapy and 18 matched healthy volunteers. Measurements The ‘beads task’, an information gathering task to assess reflection impulsivity was used and feedback learning, working memory and risk taking were also assessed. Findings Opiate dependent patients differed from controls on three out of four tasks, whereas ephedrone patients differed from controls on only one task. More specifically both patient groups were more impulsive and made more irrational choices on the beads task than controls (p<0.001). However, ephedrone patients had no deficits in working memory (p>0.1) or risk taking (p>0.1) compared with controls. Opioid dependent patients had significantly worse working memory (p<0.001) and were significantly more risk prone than controls (p=0.002). Conclusions Ephedrone patients may have similar deficits in information gathering and decision making to opiate dependent patients, with preservation of working memory and risk taking. This may reflect specific damage to anterior cingulate- basal ganglia loops.

Recently, a novel mutation in exon 24 of DNAJC13 gene (p.Asn855Ser, rs387907571) has been reported to cause autosomal dominant Parkinson’s disease (PD) in a multi-incident Mennonite family. In the present study we have sequenced the mutation containing exon of the DNAJC13 gene in a Caucasian series consisting of 1938 patients with clinical PD and 838 pathologically diagnosed Lewy Body Disease (LBD). Our sequence analysis did not identify any coding variants in exon 24 of DNAJC13. Two previously described variants in intron 23 (rs200204728 and rs2369796) were observed. Our results indicate that the region surrounding the DNAJC13 p.Asn855Ser substitution is highly conserved and mutations in this exon are not a common cause of PD or LBD among Caucasian populations.

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Parkinson’s disease (PD) is generally considered a sporadic disorder, but a strong genetic background is often found. The aim of this study was to identify the underlying genetic cause of PD in two affected siblings and to subsequently assess the role of mutations in Cathepsin B (CTSB) in susceptibility to PD. A typical PD family was identified and whole-exome sequencing was performed in two affected siblings. Variants of interest were validated using Sanger sequencing. CTSB p.Gly284Val was genotyped in 2077 PD patients and 615 unrelated healthy controls from the Czech Republic, Ireland, Poland, Ukraine, and the USA. The gene burden analysis was conducted for the CTSB gene in an additional 769 PD probands from Mayo Clinic Florida familial PD cohort. CTSB expression and activity in patient-derived fibroblasts and controls were evaluated by qRT-PCR, western blot, immunocytochemistry, and enzymatic assay. The CTSB p.Gly284Val candidate variant was only identified in affected family members. Functional analysis of CTSB patient-derived fibroblasts under basal conditions did not reveal overt changes in endogenous expression, subcellular localization, or enzymatic activity in the heterozygous carrier of the CTSB variant. The identification of the CTSB p.Gly284Val may support the hypothesis that the CTSB locus harbors variants with differing penetrance that can determine the disease risk.

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