Cathepsin B p.Gly284Val Variant in Parkinson's Disease Pathogenesis.

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.

Spinocerebellar ataxia type 6 family with phenotypic overlap with Multiple System Atrophy.

AIM OF THE STUDY: Multiple system atrophy (MSA) and spinocerebellar ataxia (SCA) share similar symptomatology. We describe a rare occurrence of familial MSA that proved to be SCA6 upon genetic analysis. MATERIALS AND METHODS: Eighty MSA patients were enrolled in our study; blood samples were collected and genetic screening of the familial case for known SCA loci was performed. RESULTS: A 68-year-old woman presented with recurrent and severe episodes of light-headedness, imbalance, frequent falls, neck and lower back stiffness, subjective arm and leg weakness, and numbness and tingling in both feet. One year later, her condition had declined; she experienced more falls, worsening instability, again more generalised but still subjective weakness, impaired fine motor movements, slurred speech, difficulty swallowing, episodes of choking, bladder incontinence, and constipation. Clinical suspicion included parkinsonism, MSA, and SCA. The patient was enrolled in our MSA study and was found to have 22 and 12 CAG repeats in CACNA1A. The other 79 clinical MSA patients were negative for SCA6 screening. CONCLUSIONS AND CLINICAL IMPLICATIONS: While MSA and SCA may have similar presentations during early disease stages, the presence of both conditions on the list of differential diagnoses can be a diagnostic dilemma. Further analysis will aid in developing a biomarker to distinguish between the two conditions and guide proper management.

TRIO gene segregation in a family with cerebellar ataxia.

AIM OF THE STUDY: To report a family with a novel TRIO gene mutation associated with phenotype of cerebellar ataxia. MATERIALS AND METHODS: Seven family members of Caribbean descent were recruited through our ataxia research protocol; of the family members, the mother and all 3 children were found to be affected with severe young-onset and rapidly progressive truncal and appendicular ataxia leading to early disability. Array comparative genomic hybridization, mitochondrial DNA analysis, and whole-exome sequencing were performed on 3 of the family members (mother and 2 daughters). RESULTS: While the maternal grandmother, great uncle and great aunt were unaffected, the mother and 3 children displayed cognitive dysfunction, severe ataxia, spasticity, and speech disturbances. Age of onset ranged between 3 and 17 years, with average current disease duration of 21 years. Whole-exome sequencing showed a variant p.A1214V in exon 22 of the TRIO gene in 3 of the family members. Array comparative genomic hybridization and mitochondrial DNA analysis were normal. The same variant was later discovered in all but one family member. CONCLUSIONS AND CLINICAL IMPLICATIONS: The TRIO p.A1214V variant is associated with cerebellar ataxia in the studied family; it was present in all affected and unaffected family members. Phenotype is severe and broad. Anticipation seems to be present (based on 2 affected generations). It is warranted to screen additional familial early-onset and rapidly progressive ataxia cases for this genotype. TRIO gene mutations may well represent a novel spinocerebellar ataxia subtype.

A novel tau mutation, p.K317N, causes globular glial tauopathy.

Globular glial tauopathies (GGTs) are 4-repeat tauopathies neuropathologically characterized by tau-positive, globular glial inclusions, including both globular oligodendroglial inclusions and globular astrocytic inclusions. No mutations have been found in 25 of the 30 GGT cases reported in the literature who have been screened for mutations in microtubule associated protein tau (MAPT). In this report, six patients with GGT (four with subtype III and two with subtype I) were screened for MAPT mutations. They included 4 men and 2 women with a mean age at death of 73 years (55-83 years) and mean age at symptomatic onset of 66 years (50-77 years). Disease duration ranged from 5 to 14 years. All were homozygous for the MAPT H1 haplotype. Three patients had a positive family history of dementia, and a novel MAPT mutation (c.951G>C, p.K317N) was identified in one of them, a patient with subtype III. Recombinant tau protein bearing the lysine-to-asparagine substitution at amino acid residue 317 was used to assess functional significance of the variant on microtubule assembly and tau filament formation. Recombinant p.K317N tau had reduced ability to promote tubulin polymerization. Recombinant 3R and 4R tau bearing the p.K317N mutation showed decreased 3R tau and increased 4R tau filament assembly. These results strongly suggest that the p.K317N variant is pathogenic. Sequencing of MAPT should be considered in patients with GGT and a family history of dementia or movement disorder. Since several individuals in our series had a positive family history but no MAPT mutation, genetic factors other than MAPT may play a role in disease pathogenesis.

SLC20A2 and THAP1 deletion in familial basal ganglia calcification with dystonia.

Idiopathic basal ganglia calcification (IBGC) is characterized by bilateral calcification of the basal ganglia associated with a spectrum of neuropsychiatric and motor syndromes. In this study, we set out to determine the frequency of the recently identified IBGC gene SLC20A2 in 27 IBGC cases from the Mayo Clinic Florida Brain Bank using both Sanger sequencing and TaqMan copy number analysis to cover the complete spectrum of possible mutations. We identified SLC20A2 pathogenic mutations in two of the 27 cases of IBGC (7 %). Sequencing analysis identified a p.S113* nonsense mutation in SLC20A2 in one case. TaqMan copy number analysis of SLC20A2 further revealed a genomic deletion in a second case, which was part of a large previously reported Canadian IBGC family with dystonia. Subsequent whole-genome sequencing in this family revealed a 563,256-bp genomic deletion with precise breakpoints on chromosome 8 affecting multiple genes including SLC20A2 and the known dystonia-related gene THAP1. The deletion co-segregated with disease in all family members. The deletion of THAP1 in addition to SLC20A2 in the Canadian IBGC family may contribute to the severe and early onset dystonia in this family. The identification of an SLC20A2 genomic deletion in a familial form of IBGC demonstrates that reduced SLC20A2 in the absence of mutant protein is sufficient to cause neurodegeneration and that previously reported SLC20A2 mutation frequencies may be underestimated.

Sequence variants in eukaryotic translation initiation factor 4-gamma (eIF4G1) are associated with Lewy body dementia.

We recently reported a missense mutation and four variants in eukaryotic translation initiation factor 4-gamma (EIF4G1) associated with parkinsonism, dementia or both. In those with a positive family history, the mode of inheritance was autosomal dominant. Detailed neuropathologic descriptions of individuals with EIF4G1 genetic variants have not been reported. Herein, we report neuropathologic findings of three individuals from two American families with EIF4G1 variants. The patients had initial clinical presentations of dementia or parkinsonism and all had dementia at the time of autopsy. One family carried an EIF4G1 double variant, c.2056G>T (p.G686C) and c.3589C>T (p.R1197 W), and one family carried variant c.1505C>T (p.A502V). All three patients also carried at least one ε4 allele of apolipoprotein E. One individual presented with cognitive impairment without significant parkinsonism; one presented with memory problems followed by bradykinesia; and the third presented with cardinal signs of Parkinson's disease, followed more than a year later by cognitive dysfunction. Pathological examination showed diffuse cortical Lewy bodies and Lewy neurites in all patients. A small subset of Lewy bodies and Lewy neurites were immunopositive for eIF4G1. All patients had moderate to frequent non-neuritic, cortical amyloid plaques, mostly medial temporal neurofibrillary pathology (Braak neurofibrillary tangle stages of II to IV), and minimal or no TDP-43 pathology. The results suggest that in some patients variants in EIF4G1 can be associated with pathology that has a high likelihood of association with clinical features of dementia with Lewy bodies.

Expanding the spectrum of KIF5A mutations-case report of a large kindred with familial ALS and overlapping syndrome.

OBJECTIVES: This paper presents the first report of amyotrophic lateral sclerosis (ALS) kindred due to the KIF5A p.Arg1007Lys, a splice-altering variant. METHODS: An index case was a 54-year-old male who developed progressive gait difficulty and imbalance followed by mild parkinsonism, spasticity, neuropathy, ataxia, and cognitive impairment with predominant subcortical frontal involvement. Brain MRI showed marked bilateral parietal lobes atrophy. Electromyography demonstrated chronic diffuse neurogenic changes. Due to the positive history of similar symptoms in his father and the diagnosis of ALS in 10 other family members, extensive genetic testing was pursued. RESULTS: Genetic screening for GRN, C9orf72, TARDBP, SOD1, FUS, MAPT mutations, and hereditary ataxia panel, was unremarkable. Whole-exome sequencing revealed c.3020G > A (p.Arg1007Lys) mutation in the KIF5A gene, later confirmed in two affected relatives. DISCUSSION: Similar to previous reports on KIF5A-related ALS, our index case, had a mild disease course with prolonged survival. However, as the rate of progression and survival time differed even among the same family members, other factors were probably at play. Additionally, our index case and his father displayed features overlapping ALS, spastic paraplegia, Charcot-Marie-Tooth disease type 2, and frontotemporal dementia. Therefore, we suggest considering KIF5A mutations in the differential diagnosis, particularly in the presence of overlapping features of spasticity, neuropathy, cerebellar ataxia, and dementia.

Perry syndrome: Novel DCTN1 mutation in a large kindred and first observation of prodromal disease.

INTRODUCTION: Perry syndrome (PS) is a hereditary neurodegenerative disorder caused by mutations in the DCTN1 gene and characterized by TDP-43 pathology. As the diagnosis is usually made at the advanced stages of the disease, there are no studies on the asymptomatic mutation carriers and their conversion to overt disease. METHODS: We personally examined 27 members of the large kindred of 104 individuals with familial parkinsonism. We evaluated each case with clinical (neurological examination; motor and non-motor scales), genetic testing (whole-exome or Sanger sequencing), and laboratory (neurofilament light, NFL; glial fibrillary acidic protein, GFAP) measures. Autopsy study was done on two individuals. RESULTS: The mean age at evaluation was 49 years. Comorbidities were present in 20 cases, including sleep problems (n = 15 total, sleep apnea in 7), dysautonomia (n = 10), weight loss (n = 8), and anxiety/depression (n = 8). Neurological abnormalities were present in 18, including parkinsonism (n = 7), isolated tremor (n = 2), and varied isolated signs in individual cases. Cognition and smell were preserved. Genetic testing revealed a novel c.200G > T (Gly67Val) mutation in the DCTN1 gene in 10 individuals. The mutation, segregated with the PS phenotype (n = 4), was absent in gnomAD, and in silico predictions indicated it was pathogenic. Three young mutation carriers were monosymptomatic (prodromal), and three were asymptomatic. Plasma NFL and GFAP values were similar among the cases. Autopsy studies showed typical PS neuropathological findings. CONCLUSIONS: We identified a novel pathogenic Gly67Val DCTN1 mutation. We report prodromal disease of PS in some mutation carriers; however, more investigation is necessary to confirm this observation.

Crohn's and Parkinson's Disease-Associated LRRK2 Mutations Alter Type II Interferon Responses in Human CD14+ Blood Monocytes Ex Vivo.

The Leucine Rich Repeat Kinase 2 (LRRK2) is one of causative genes of familial Parkinson's disease (PD). The M2397T polymorphism in LRRK2 is genetically associated with sporadic Crohn's disease (CD). LRRK2 is expressed in human CD14+ monocytes, induced by interferon-γ (IFN-γ) and suppresses inflammatory activation. We hypothesize that IFN-γ-induced LRRK2 and inflammatory gene expression is altered by LRRK2 genetic polymorphism found in CD and PD cases. A total of 46 CD and 51 control cases, and 16 PD cases and 16 PD-linked LRRK2 mutation cases were recruited. Live human CD14+ monocytes were isolated from donors for ex vivo IFN-γ stimulation and gene expression analysis. IFN-γ potently enhanced TNFA, IL12, HLADRA1 and LRRK2 expression, which was suppressed by FK506, a calcineurin-specific inhibitor, but further enhanced by LRRK2-specific kinase inhibitor (GSK2578215A). The 2397-M/M CD risk allele enhanced IFN-γ responses of CD14+ cells in CD but not in control group. CD14+ monocytes from G2019S and R1441C LRRK2 mutated PD cases and carriers show no changes in IFN-γ responses for TNFA or IL12, reduced response for HLADRA1, and enhanced responses for LRRK2 in FK506-sensitive manner. These data demonstrate that CD-associated LRRK2 mutations are significant modifiers of innate immune response in CD14+ monocytes, and PD-associated LRRK2 mutation may contribute to reduced antigen presentation response. Graphical Abstract.

Early-Onset Parkinson Disease Screening in Patients From Nigeria.

Introduction: Nigeria is one of the most populated countries in the world; however, there is a scarcity of studies in patients with age-related neurodegenerative diseases, such as Parkinson disease (PD). The aim of this study was to screen patients with PD including a small cohort of early-onset PD (EOPD) cases from Nigeria for PRKN, PINK1, DJ1, SNCA multiplication, and LRRK2 p.G2019S. Methods: We assembled a cohort of 109 Nigerian patients with PD from the four main Nigerian tribes: Yoruba, Igbo, Edo, and Hausa. Fifteen cases [14 from the Yoruba tribe (93.3%)] had EOPD (defined as age-at-onset <50 years). All patients with EOPD were sequenced for the coding regions of PRKN, PINK1, and DJ1. Exon dosage analysis was performed with a multiplex ligation-dependent probe amplification assay, which also included a SNCA probe and LRRK2 p.G2019S. We screened for LRRK2 p.G2019S in the entire PD cohort using a genotyping assay. The PINK1 p.R501Q functional analysis was conducted. Results: In 15 patients with EOPD, 22 variants were observed [PRKN, 9 (40.9%); PINK1, 10 (45.5%); and DJ1, 3 (13.6%)]. Three (13.6%) rare, nonsynonymous variants were identified, but no homozygous or compound heterozygous carriers were found. No exonic rearrangements were present in the three genes, and no carriers of SNCA genomic multiplications or LRRK2 p.G2019S were identified. The PINK1 p.R501Q functional analysis revealed pathogenic loss of function. Conclusion: More studies on age-related neurodegenerative diseases are needed in sub-Saharan African countries, including Nigeria. Population-specific variation may provide insight into the genes involved in PD in the local population but may also contribute to larger studiesperformed in White and Asian populations.

MR imaging of brainstem atrophy in progressive supranuclear palsy.

BACKGROUND: To enhance the sensitivity and specificity of the clinical diagnosis of progressive supranuclear palsy (PSP), neuroradiological parameters established in pathologically proven cases are needed. METHODS: We examined brainstem atrophy in five pathologically confirmed PSP patients (three men, mean age at death 77 years, range 64-84 years). Time interval between symptom onset and MRI ranged from 1 to 5 years, and between MRI and death from 33 to 52 months. Only one patient had clinical diagnosis of PSP at the time of MRI. Control group consisted of 19 age- and gender-matched healthy subjects. Seventeen morphometric parameters of the midbrain and pons were measured on T1-weighted midsagittal and T2-weighted axial MRI scans with Image Analyzer. Measurements of superior cerebellar peduncle (SCP) width were performed on PSP autopsy specimens. RESULTS: Mean SCP width on MRI in PSP (2.7 +/- 0.8 mm, 95%CI: 2.1-3.3) was smaller than in controls (3.7 +/- 0.5 mm, 95%CI: 3.5-3.9). Mean SCP width at autopsy was 8% smaller than mean SCP width on MRI. Midsagittal midbrain area in PSP (99.1 +/- 6.9 mm(2), 95%CI: 90.5-107.6) was smaller than in controls (141.0 +/- 18.1 mm(2), 95%CI: 132.2-149.7). Midbrain/pons area ratio in PSP was 1:5 and in controls was 1:4 (p < 0.01). Repeat MRI 17 months later in one PSP case revealed 30% decrease of SCP width. CONCLUSIONS: MR imaging with quantitative analysis may be useful in the diagnosis of early PSP and in monitoring disease course.

Comparison of clinical features among Parkinson's disease subtypes: A large retrospective study in a single center.

INTRODUCTION: Tremor dominant (TD), postural instability/gait difficulty (PIGD), and akinetic-rigid (AR) subtypes are widely used in classifying patients with Parkinson's disease (PD). METHODS: We compared clinical characteristics between PD subtypes in a large retrospective cohort. Between 1998 and 2016, we included a total of 1003 patients with PD in this retrospective study. Six hundred ninety-four patients had more than one visit. Data were collected regarding motor/non-motor symptoms at the initial/final visits. Based on the prominent symptom at the initial visit, we classified patients into one of the four subtypes: TD, AR, gait difficulty, and mixed. Rapid progression was defined by emergence of falls, dementia, or dependency within 5years after onset. RESULTS: TD was the most prevalent subtype (44%), followed by AR (29%), mixed (18%), and gait difficulty (9%). Rapid progression was observed more frequently in gait difficulty compared to AR (OR: 3.59 P<0.001). Hallucinations at the final visit were more likely to occur in AR (OR: 2.36, P=0.005) and mixed (OR: 3.28, P<0.001) compared to TD. CONCLUSIONS: Our findings provide support for a distinction of four different PD subtypes: TD, AR, gait difficulty, and mixed. The gait difficulty subtype was distinguishable from the AR subtype.

Clinical-pathologic study of biomarkers in FTDP-17 (PPND family with N279K tau mutation).

The objective of this clinical-pathologic study was to identify biomarkers for a pallidopontonigral degeneration (PPND) kindred of frontotemporal dementia and parkinsonism linked to chromosome 17 (FTDP-17) harboring the N279K tau mutation. Five affected subjects, one at-risk who later became symptomatic, and one at-risk asymptomatic mutation carrier, had abnormal (18)fluorodeoxyglucose PET demonstrating asymmetric temporal lobe hypometabolism. All except the asymptomatic mutation carrier had abnormal brain MRI. Parkinsonism, myoclonus, anosmia, insomnia, speech, and autonomic dysfunction were identified. Autopsy of six affected subjects showed frontotemporal degeneration with extensive tauopathy. Further studies of FTDP-17 patients are needed to replicate these findings.

Occurrence of Crohn's disease with Parkinson's disease.

We retrospectively investigated the co-occurrence of Crohn's disease in a cohort of 876 patients with Parkinson's disease, based on the observation that LRRK2 is a shared genetic risk factor. We identified 2 patients with Crohn's disease; this number was consistent with the number of cases expected in the general population.

RAB39B gene mutations are not a common cause of Parkinson's disease or dementia with Lewy bodies.

Mutations in Ras-related protein Rab-39B (RAB39B) gene have been linked to X-linked early-onset Parkinsonism with intellectual disabilities. The aim of this study was to address the genetic contribution of RAB39B to Parkinson's disease (PD), dementia with Lewy bodies (DLB), and pathologically confirmed Lewy body dementia (pLBD) cases. A cohort of 884 PD, 399 DLB, and 379 pLBD patients were screened for RAB39B mutations, but no coding variants were found, suggesting RAB39B mutations are not a common cause of PD, DLB, or pLBD in Caucasian population.

Whole-exome sequencing as a diagnostic tool in a family with episodic ataxia type 1.

Complex neurologic phenotypes are inherently difficult to diagnose. Whole-exome sequencing (WES) is a new tool in the neurologist's diagnostic armamentarium. Whole-exome sequencing can be applied to investigate the "diagnostic odyssey" cases. These cases involve patients with rare diseases that likely have a genetic etiology but have failed to be diagnosed by clinical evaluation and targeted gene testing. We describe such a case, a 22-year-old man who had mild intellectual developmental disability and episodes of jerking ataxic movements that affected his whole body. He underwent numerous multidisciplinary and multicentric evaluations throughout his life that failed to establish a clear diagnosis. Following his visit to Mayo Clinic in Jacksonville, Florida, WES was applied for genetic determination of the unknown disorder in the proband and his biological parents and sister. Additional clinical evaluation, magnetic resonance neuroimaging, electromyography, and electroencephalography of the proband were performed to verify the phenotype after the WES results were available. To our knowledge, this is the first report of the application of WES to facilitate the diagnosis of episodic ataxia type 1. This case illustrates that WES supported by clinical data is a useful and time-saving tool in the evaluation of patients with rare and complex hereditary disorders.

Frontotemporal dementia-associated N279K tau mutant disrupts subcellular vesicle trafficking and induces cellular stress in iPSC-derived neural stem cells.

BACKGROUND: Pallido-ponto-nigral degeneration (PPND), a major subtype of frontotemporal dementia with parkinsonism related to chromosome 17 (FTDP-17), is a progressive and terminal neurodegenerative disease caused by c.837 T > G mutation in the MAPT gene encoding microtubule-associated protein tau (rs63750756; N279K). This MAPT mutation induces alternative splicing of exon 10, resulting in a modification of microtubule-binding region of tau. Although mutations in the MAPT gene have been linked to multiple tauopathies including Alzheimer's disease, frontotemporal dementia and progressive supranuclear palsy, knowledge regarding how tau N279K mutation causes PPND/FTDP-17 is limited. RESULTS: We investigated the underlying disease mechanism associated with the N279K tau mutation using PPND/FTDP-17 patient-derived induced pluripotent stem cells (iPSCs) and autopsy brains. In iPSC-derived neural stem cells (NSCs), the N279K tau mutation induced an increased ratio of 4-repeat to 3-repeat tau and accumulation of stress granules indicating elevated cellular stress. More significant, NSCs derived from patients with the N279K tau mutation displayed impaired endocytic trafficking as evidenced by accumulation of endosomes and exosomes, and a reduction of lysosomes. Since there were no significant differences in cellular stress and distribution of subcellular organelles between control and N279K skin fibroblasts, N279K-related vesicle trafficking defects are likely specific to the neuronal lineage. Consistently, the levels of intracellular/luminal vesicle and exosome marker flotillin-1 were significantly increased in frontal and temporal cortices of PPND/FTDP-17 patients with the N279K tau mutation, events that were not seen in the occipital cortex which is the most spared cortical region in the patients. CONCLUSION: Together, our results demonstrate that alterations of intracellular vesicle trafficking in NSCs/neurons likely contribute to neurodegeneration as an important disease mechanism underlying the N279K tau mutation in PPND/FTDP-17.

Three sib-pairs of autopsy-confirmed progressive supranuclear palsy.

OBJECTIVE: To describe the clinical, pathological, and genetic features of three sib-pairs of pathologically-confirmed progressive supranuclear palsy (PSP). METHODS: We searched the Mayo Clinic neurodegenerative diseases brain bank for cases of PSP in which more than one family member had pathologically-confirmed PSP. Clinical and pathological data were reviewed and all individuals were screened for mutations in MAPT, by sequencing exons 1, 7, and 9-13. RESULTS: We identified three sib-pairs of pathologically-confirmed PSP. Sufficient information was available to suggest an autosomal dominant inheritance in two. The mean age at symptom onset was 41 years in one pair, and 76 years in the other two. The young onset pair had a p.S285R mutation in MAPT, but no mutations were detected in the other two. CONCLUSIONS: All sib-pairs had typical pathological features of PSP; however, the age at onset of the sib-pair with MAPT mutation was significantly younger than sporadic PSP. Future studies are warranted to identify a possible genetic basis for PSP associated with late onset and typical PSP pathology.

Mitochondrial targeting sequence variants of the CHCHD2 gene are a risk for Lewy body disorders.

OBJECTIVE: To assess the role of CHCHD2 variants in patients with Parkinson disease (PD) and Lewy body disease (LBD) in Caucasian populations. METHODS: All exons of the CHCHD2 gene were sequenced in a US Caucasian patient-control series (878 PD, 610 LBD, and 717 controls). Subsequently, exons 1 and 2 were sequenced in an Irish series (355 PD and 365 controls) and a Polish series (394 PD and 350 controls). Immunohistochemistry and immunofluorescence studies were performed on pathologic LBD cases with rare CHCHD2 variants. RESULTS: We identified 9 rare exonic variants of unknown significance. These variants were more frequent in the combined group of PD and LBD patients compared to controls (0.6% vs 0.1%, p = 0.013). In addition, the presence of any rare variant was more common in patients with LBD (2.5% vs 1.0%, p = 0.050) compared to controls. Eight of these 9 variants were located within the gene's mitochondrial targeting sequence. CONCLUSIONS: Although the role of variants of the CHCHD2 gene in PD and LBD remains to be further elucidated, the rare variants in the mitochondrial targeting sequence may be a risk factor for Lewy body disorders, which may link CHCHD2 to other genetic forms of parkinsonism with mitochondrial dysfunction.