Atypical findings: Atypical parkinsonian syndromes or Atypical parkinsonian syndromes look-alikes.

OBJECTIVE: In parkinsonian syndromes, presentations other than current diagnostic criteria are considered atypical findings. Our goal was to identify and describe the frequency and features of uncommon manifestations of atypical parkinsonian syndromes within our group. METHODS: We retrospectively retrieved the medical records of all patients admitted to our clinic with parkinsonism between January 2011 and January 2022. We only included patients with atypical parkinsonian syndromes, in which the diagnosis was based on current clinical criteria. We retrospectively analyzed neurological, psychiatric, radiological, and electrophysiological characteristics. Typical and atypical features were classified according to the current clinical criteria and previous reports. RESULTS: We determined 51 patients with atypical parkinsonian syndromes; 46 were included, whereas five were excluded due to insufficient follow-up. The probable diagnoses were multiple system atrophy (MSA, n = 19), dementia with Lewy bodies (DLB, n = 10), frontotemporal dementia (FTD, n = 10), corticobasal syndrome (CBS, n = 3), progressive supranuclear palsy (PSP, n = 4). The prevalence of atypical findings was similar among different types of atypical parkinsonian syndromes (p = 0.847). Atypical findings were eyelid myoclonus, double vision in MSA; ataxia, myoclonus, and a typical hummingbird sign on MRI in DLB; pyramidal findings and family history in FTD; early onset, family history, and onset with psychiatric findings in PSP-like phenotype. Genetic causes were identified in the FTD-like phenotype with pyramidal findings, whereas symptom onset was early with myoclonus in the PSP-like phenotype. CONCLUSION: Atypical findings such as abnormal saccades, myoclonus, and ataxia may be a part of degenerative syndromes. However, family history, onset at an earlier age, and specific neurological findings suggest genetic syndromes.

Parainfectious autoimmune encephalitis related to SARS-CoV-2 infection, presenting with catatonia.

OBJECTIVE: SARS-CoV-2 infection commonly affects both the central and peripheral nervous systems, resulting in a variety of neurological and psychiatric symptoms. Whereas the effects of SARS-CoV-2 on neuronal structures in the short and long-term are still controversial, neurological involvement secondary to SARS-CoV- 2 is heterogeneous in terms of clinical presentation, treatment response, and prognosis. METHOD: A case of autoimmune encephalitis developing after SARS-CoV-2 is described in this article. RESULTS: The patient was admitted to the clinic with classical signs of catatonia and encephalopathy. The emergence of neuropsychiatric problems after the relief of SARS-CoV-2 symptoms suggests that symptoms were primarily related to immune processes. This patient demonstrated a good clinical response to symptomatic catatonia treatment and immune-modulatory agents and recovered both physically and cognitively without sequelae. CONCLUSION: SARS-CoV-2 infection may involve encephalitic involvement and psychological symptoms (including catatonia) after the infection by triggering autoimmune pathways.

Ataxia in a Movement Disorders Outpatient Clinic: a Single-Center Experience in Turkey.

The etiology may not be determined in patients with ataxia despite detailed evaluations. The aim of this study was to investigate the clinical and laboratory characteristics of a large cohort of patients with adult-onset ataxia of different etiologies, particularly, undetermined etiologies despite extensive clinical, genetic, laboratory, electrophysiological, and imaging investigations. The medical records of all patients diagnosed with ataxia of subacute-chronic onset between January 2011 and March 2021 were reviewed retrospectively. The records of patients with symptom onset after 16 years of age were included in the study. In all patients, clinical and demographic findings were noted. Etiologies were classified as acquired, hereditary, degenerative (multiple system atrophy-cerebellar, MSA-C), functional, and undetermined. During the study period, we determined 74 patients with ataxia and 59 (35 males) patients met the study criteria. The age range was 22-87 years. The etiologies were hereditary (n = 19), acquired (n = 14), MSA-C (n = 9), functional (n = 2), and undetermined (n = 15). The patients with hereditary etiologies and undetermined causes were significantly younger at admission and at symptom onset (p = 0.001 and p = 0.000). There was a significant delay until diagnosis in patients with hereditary etiologies compared to other etiologies. In acquired etiologies, axial findings (71.4%) were more prominent whereas extremity and axial findings were more common in patients with hereditary etiologies (83.3%, p = 0.030). There were systemic and radiological indicators such as hearing loss, juvenile cataract, or dentate hyperintensity in certain disorders. Hereditary etiologies are as common as acquired or degenerative etiologies in adults. However, they have an earlier onset and delayed diagnosis. Therefore, we should recognize the extracerebellar neurological, systemic, and neuroimaging findings.

[Comparison of long-latency reflex and mixed nerve silent period responses in various hypokinetic movement disorders]. / A hosszú latenciájú reflexválaszoknak és a kevert idegek csendes periódusainak összehasonlítása különbözo hipokinetikus mozgási rendellenességekben.

Background and purpose: Long-latency reflex and mixed nerve silent period responses are electrophysiological methods to study the sensorimotor functions of the central nervous system. Here we aimed to study long-latency reflexes and mixed nerve silent period responses in different types of hypokinetic movement disorders in order to find an electrophysiological landmark to distinguish them. Methods: We included 39 patients with idiopathic Parkinson's disease (IPD), 12 patients with multiple system atrophy (MSA), 10 patients with corticobasal syndrome (CBS), 5 patients with progressive supranuclear palsy (PSP) and 26 healthy participants. We recorded the segmental reflex, the long-latency reflexes and the mixed nerve silent period responses for each participant. Results: C reflex, long-latency reflex-I and long-latency reflex-III responses were not obtained in any patients with PSP. Long-latency reflex amplitude/ F amplitude ratio was significantly lower in patients with IPD and PSP compared to healthy individuals (p=0.036, p=0.006 respectively). The mixed nerve silent period end latencies were significantly longer in IPD, MSA, CBS groups compared to the healthy individuals (p=0.026, p=0.050, p=0.008 respectively). Conclusion: We suggest that recording long-latency reflex, particularly C reflex responses may provide promising results in distinction of CBS and MSA from PSP. Prospective studies with clinical findings and brainstem reflexes may offer more information.

ADCY5 gene mutation: a case report.

BACKGROUND: ADCY5 mutation is a clinical condition that has been described in limited numbers in the literature, causing hyperkinetic movement disorder, and may be sporadic or familial. PATIENT DESCRIPTION: This report looks at the involuntary movements that started early in life in a 5-year-old girl. RESULTS: Patient's electroensephalogram and cranial magnetic resonance imaging were normal. Metabolic scans were normal. ADCY5 mutation was found in whole exome sequencing of the patient who did not have a similar family history. CONCLUSION: Some features such as the worsening of involuntary movements after sleep and the presence of hypotonia in our patient suggested this mutation. Our patient is resistant to more than one drug. With this report, we aimed to pave the way for better understanding of the gene and the discovery of different treatment options.

Prevalence of clinical manifestations and neuroimaging features in cerebral small vessel disease.

BACKGROUND AND PURPOSE: Cerebral small vessel disease (CSVD) may present with gradual onset, chronic parkinsonism and/or dementia. In this study, we aimed to identify the prevalence and clinical characteristics of apathy, dementia and parkinsonism in a cohort of patients with CSVD and to determine the neuroimaging features in these patients. METHODS: We included all patients with CSVD, who were admitted to the stroke outpatient clinic between February 2018 and February 2019. All patients were over 18 years of age. Demographic, clinical and neuoimaging findings were noted. Detailed neurological examination and neuropsychiatric assessments were done in each patient. The types and anatomical sites of lesions in neuroimaging were also determined. RESULTS: Among all stroke patients in the study period, CSVD constituted 23.3%. The etiologies were possible arteriosclerotic, amyloid angiopathy and CADASIL in 85.0%, 3.3% and 11.7% of these patients, respectively. The most common clinical feature was apathy followed by dementia, parkinsonism, and parkinsonism plus dementia. In regression analysis, apathy and parkinsonism was associated with lesions in caudate or in other basal ganglia structures whereas lesions of corpus callosum increased the risk of dementia. Hypertension was also associated with the presence of dementia. There was no specific association between the type of lesion in neuroimaging and clinical findings. CONCLUSIONS: The risk of clinical manifestations such as apathy, dementia and parkinsonism is high in CSVD. Involvement of basal ganglia increased the risk of parkinsonism and apathy whereas involvement of corpus callosum increased the risk of dementia. A detailed assessment for apathy is necessary along with parkinsonism and cognitive findings since apathy is the most common finding in CSVD.

Hand Pronation-Supination Movement as a Proxy for Remotely Monitoring Gait and Posture Stability in Parkinson's Disease.

The Unified Parkinson's Disease Rating Scale (UPDRS) is a subjective Parkinson's Disease (PD) physician scoring/monitoring system. To date, there is no single upper limb wearable/non-contact system that can be used objectively to assess all UPDRS-III motor system subgroups (i.e., tremor (T), rigidity (R), bradykinesia (B), gait and posture (GP), and bulbar anomalies (BA)). We evaluated the use of a non-contact hand motion tracking system for potential extraction of GP information using forearm pronation-supination (P/S) motion parameters (speed, acceleration, and frequency). Twenty-four patients with idiopathic PD participated, and their UPDRS data were recorded bilaterally by physicians. Pearson's correlation, regression analyses, and Monte Carlo validation was conducted for all combinations of UPDRS subgroups versus motion parameters. In the 262,125 regression models that were trained and tested, the models within 1% of the lowest error showed that the frequency of P/S contributes to approximately one third of all models; while speed and acceleration also contribute significantly to the prediction of GP from the left-hand motion of right handed patients. In short, the P/S better indicated GP when performed with the non-dominant hand. There was also a significant negative correlation (with medium to large effect size, range: 0.3-0.58) between the P/S speed and the single BA score for both forearms and combined UPDRS score for the dominant hand. This study highlights the potential use of wearable or non-contact systems for forearm P/S to remotely monitor and predict the GP information in PD.

Genetic variants of vitamin D metabolism-related DHCR7/NADSYN1 locus and CYP2R1 gene are associated with clinical features of Parkinson's disease.

PURPOSE/AIM OF THE STUDY: Parkinson's disease (PD) is the second most common neurodegenerative disorder. Vitamin D deficiency is suggested to be related to PD. A genome-wide association study indicated that genes involved in vitamin D metabolism affect vitamin D levels. Among these genes, single nucleotide polymorphisms (SNPs) of the vitamin D receptor (VDR) and vitamin D binding protein (VDBP/GC) genes have also been demonstrated to be associated with PD risk. Our aim was to investigate the relevance of SNPs within the 7-dehydrocholesterol reductase/nicotinamide adenine dinucleotide synthetase 1 (DHCR7/NADSYN1) locus and vitamin D 25-hydroxylase (CYP2R1) gene, which encode important enzymes that play a role in the vitamin D synthesis pathway, with PD and its clinical features. MATERIALS AND METHODS: Genotypes of 382 PD patients and 240 cognitively healthy individuals were evaluated by a LightSNiP assay for a total of 10 SNPs within the DHCR7/NADSYN1 locus and CYP2R1 gene. RESULTS: There were no significant differences in the allele and genotype distributions of any of the SNPs between any patient groups and healthy subjects. However, our results indicated that all of the SNPs within the DHCR7/NADSYN1 locus and CYP2R1 gene, except rs1993116, were associated with clinical motor features of PD including initial predominant symptom, freezing of gait (FoG) and falls as well as disease stage and duration of the disease. CONCLUSIONS: In conclusion, genetic variants of the DHCR7/NADSYN1 locus and the CYP2R1 gene might be related to the inefficient utilization of vitamin D independent from vitamin D levels, and it might result in differences in the clinical features of PD patients.

The Complex Genetic Landscape of Hereditary Ataxias in Turkey and Implications in Clinical Practice.

BACKGROUND: The genetic and epidemiological features of hereditary ataxias have been reported in several populations; however, Turkey is still unexplored. Due to high consanguinity, recessive ataxias are more common in Turkey than in Western European populations. OBJECTIVE: To identify the prevalence and genetic structure of hereditary ataxias in the Turkish population. METHODS: Our cohort consisted of 1296 index cases and 324 affected family members. Polymerase chain reaction followed by Sanger sequencing or fragment analysis were performed to screen for the trinucleotide repeat expansions in families with a dominant inheritance pattern, as well as in sporadic cases. The expansion in the frataxin (FXN) gene was tested in all autosomal recessive cases and in sporadic cases with a compatible phenotype. Whole-exome sequencing was applied to 251 probands, selected based on the family history, age of onset, and phenotype. RESULTS: Mutations in known ataxia genes were identified in 30% of 1296 probands. Friedreich's ataxia was found to be the most common recessive ataxia in Turkey, followed by autosomal recessive spastic ataxia of Charlevoix-Saguenay. Spinocerebellar ataxia types 2 and 1 were the most common dominant ataxias. Whole-exome sequencing was performed in 251 probands with an approximate diagnostic yield of 50%. Forty-eight novel variants were found in a plethora of genes, suggesting a high heterogeneity. Variants of unknown significance were discussed in light of clinical data. CONCLUSION: With the large sample size recruited across the country, we consider that our results provide an accurate picture of the frequency of hereditary ataxias in Turkey. © 2021 International Parkinson and Movement Disorder Society.

Low Levels of LRRK2 Gene Expression are Associated with LRRK2 SNPs and Contribute to Parkinson's Disease Progression.

Parkinson's disease (PD) is a chronic neurodegenerative disease that has relatively slow progression with motor symptoms. Leucine-rich repeat kinase 2 (LRRK2) gene mutations and polymorphisms are suggested to be associated with PD. In this study, we aimed to investigate the association between single-nucleotide polymorphisms (SNPs) of the LRRK2 gene, namely, rs11176013, rs10878371, rs11835105, and PD. Genotypes of 132 PD cases and 133 healthy individuals were determined by qRT-PCR. Haplotype analysis was performed. Additionally, LRRK2 mRNA expression levels were determined in 83 PD cases and 55 healthy subjects. The relationship between LRRK2 mRNA levels, the target SNPs, and clinical data was also investigated. Our results indicated that the "GG" genotype and "G" allele of rs11176013 and the "CC" genotype and "C" allele of rs10878371 were more frequent in cases. The "GCG" haplotype was significantly more frequent in cases. LRRK2 mRNA expression levels in patients were significantly lower than those in healthy individuals. The patients with the "CC" genotype for rs10878371 and the "GG" genotype for rs11176013 had decreased LRRK2 mRNA levels. We found that the rs11176013 "GG" genotype and the rs10878371 "CC" genotype were less frequently seen in cases with akinetic rigid or combined akinetic rigid and tremor-dominant initial symptoms. Consequently, our results demonstrate that the rs11176013 and rs10878371 polymorphisms are associated with PD in a Turkish cohort, and moreover, these results suggest that these polymorphisms may affect the expression of the LRRK2 gene and disease progression and thus play a role in the pathogenesis of PD.

Intrinsic Auricular Muscle Zone Stimulation Improves Walking Parameters of Parkinson's Patients Faster Than Levodopa in the Motion Capture Analysis: A Pilot Study.

It has been demonstrated that intrinsic auricular muscles zone stimulation (IAMZS) can improve the motor symptoms of Parkinson's disease (PD) patients who are examined with the Unified Parkinson's Disease Rating Scale (UPDRS) motor scores. In the present pilot study, using motion capture technology, we aimed to investigate the efficacy of IAMZS compared to medication alone or in combination with medication. Ten PD patients (mean age: 54.8 ± 10.1 years) were enrolled. Each participant participated in three different sessions: sole medication, sole stimulation-20 min of IAMZS, and combined IAMZS (20 min) and medication. Each session was performed on different days but at the same time to be aligned with patients' drug intake. Motion capture recording sessions took place at baseline, 20, 40, and 60 min. Statistical analysis was conducted using one-way repeated measures ANOVA. Bonferroni correction was implemented for pairwise comparisons. The sole medication was ineffective to improve gait-related parameters of stride length, stride velocity, stance, swing, and turning speed. In the sole-stimulation group, pace-related gait parameters were significantly increased at 20 and 40 min. These improvements were observed in stride length at 20 (p = 0.0498) and 40 (p = 0.03) min, and also in the normalized stride velocity at 40 min (p-value = 0.02). Stride velocity also tended to be significant at 20 min (p = 0.06) in the sole-stimulation group. Combined IAMZS and medication demonstrated significant improvements in all the time segments for pace-related gait parameters [stride length: 20 min (p = 0.04), 40 min (p = 0.01), and 60 min (p < 0.01); stride velocity: 20 min (p < 0.01), 40 min (p = 0.01), and 60 min (p < 0.01)]. These findings demonstrated the fast action of the IAMZS on PD motor symptoms. Moreover, following the termination of IAMZS, a prolonged improvement in symptoms was observed at 40 min. The combined use of IAMZS with medication showed the most profound improvements. The IAMZS may be particularly useful during medication off periods and may also postpone the long-term side effects of high-dose levodopa. A large scale multicentric trial is required to validate the results obtained from this pilot study. Clinical Trial Registration: www.ClinicalTrials.gov, identifier NCT03907007.

Myoclonus in the elderly: A retrospective analysis of clinical and electrophysiological characteristics of patients referred to an electrophysiology laboratory.

BACKGROUND AND OBJECTIVE: Late-onset myoclonus in the elderly is mainly related to dementia or systemic disease. In this report, we aimed to investigate the clinical and electrophysiological features of patients with late-onset myoclonus. PATIENTS AND METHOD: We retrospectively assessed the medical records of patients who were referred to our electromyography laboratory. From these records, we included all patients who had myoclonus which started after the age of 60 years and in whom it was confirmed by polymyography. Demographic, clinical and electrophysiological findings were retrieved from the medical records. RESULTS: There were 63 patients with myoclonus. Types of myoclonus were spinal segmental (n = 2), cortical (n = 25) and probable cortico-subcortical involving upper extremities (n = 36). The latter two types displayed reflex sensitivity. Four patients (one with multifocal cortical myoclonus and others with probable cortico-subcortical myoclonus) were diagnosed with probable CJD. Other diagnoses were Parkinsons's disease, Parkinson-plus or dementia syndromes, vascular parkinsonism, polyneuropathy, Celiac disease and post-hypoxic encephalopathy. Eleven patients did not have a specific diagnosis. CONCLUSIONS: Myoclonus in our cohort was mostly associated with parkinsonism. Cortical myoclonus is not rare in the elderly age group. Myoclonus in polyneuropathy is irregular, tremor-like with electrophysiological characteristics similar to the cortical subtype.

Electrophysiological Investigations in Orthostatic Myoclonus: Preliminary Findings.

We report the clinical and electrophysiological findings in seven patients with orthostatic myoclonus (OM) associated with gait initiation failure and falls. OM is one of the causes of unsteadiness of stance and gait, and it may develop as a symptom of neurodegenerative disorders. Both positive myoclonic bursts and negative myoclonus may be seen in electrophysiological recordings, and electrophysiological analysis suggests a subcortical origin for OM.

Rapid Alleviation of Parkinson's Disease Symptoms via Electrostimulation of Intrinsic Auricular Muscle Zones.

Background: Deep brain stimulation of the subthalamic nucleus (STN-DBS) and the pedunculopontine nucleus (PPN) significantly improve cardinal motor symptoms and postural instability and gait difficulty, respectively, in Parkinson's disease (PD). Objective and Hypothesis: Intrinsic auricular muscle zones (IAMZs) allow the potential to simultaneously stimulate the C2 spinal nerve, the trigeminal nerve, the facial nerve, and sympathetic and parasympathetic nerves in addition to providing muscle feedback and control areas including the STN, the PPN and mesencephalic locomotor regions. Our aim was to observe the clinical responses to IAMZ stimulation in PD patients. Method: Unilateral stimulation of an IAMZ, which includes muscle fibers for proprioception, the facial nerve, and C2, trigeminal and autonomic nerve fibers, at 130 Hz was performed in a placebo- and sham-controlled, double-blinded, within design, two-armed study of 24 PD patients. Results: The results of the first arm (10 patients) of the present study demonstrated a substantial improvement in Unified Parkinson's Disease Ratings Scale (UPDRS) motor scores due to 10 min of IAMZ electrostimulation (p = 0.0003, power: 0.99) compared to the placebo control (p = 0.130). A moderate to large clinical difference in the improvement in UPDRS motor scores was observed in the IAMZ electrostimulation group. The results of the second arm (14 patients) demonstrated significant improvements with dry needling (p = 0.011) and electrostimulation of the IAMZ (p < 0.001) but not with sham electrostimulation (p = 0.748). In addition, there was a significantly greater improvement in UPDRS motor scores in the IAMZ electrostimulation group compared to the IAMZ dry needling group (p < 0.001) and the sham electrostimulation (p < 0.001) groups. The improvement in UPDRS motor scores of the IAMZ electrostimulation group (ΔUPDRS = 5.29) reached moderate to high clinical significance, which was not the case for the dry needling group (ΔUPDRS = 1.54). In addition, both arms of the study demonstrated bilateral improvements in motor symptoms in response to unilateral IAMZ electrostimulation. Conclusion: The present study is the first demonstration of a potential role of IAMZ electrical stimulation in improving the clinical motor symptoms of PD patients in the short term.

Brainstem reflexes are hyperactive in patients with drug-induced akathisia.

Akathisia is a sensori-motor phenomenon which is generally encountered as an adverse effect of antidopaminergic medications suggesting involvement of dopaminergic pathways. We recently showed nociceptive flexor reflex was altered in akathisia as compared to restless legs syndrome and therefore, these findings may indicate co-involvement of pathways other than dopaminergic ones. To examine functional status of different pathways, we investigated auditory startle reflex (ASR), startle response to somatosensory input (SSS), and trigemino-cervical reflex (TCR) in a group of patients with akathisia. Consecutive seven patients with drug-induced akathisia and age- and gender-matched healthy subjects were prospectively included in the study. The diagnosis was made by appropriate clinical criteria. Brainstem reflexes, ASR, SSS, and TCR were examined in all participants. The probability, onset latency, amplitude, and duration were measured and compared between groups. The probability and amplitudes of ASRs were significantly increased and durations of ASRs and TCRs were prolonged in the patient group. Latencies of all responses as well as patterns of startle responses were similar between groups. The results reveal hyperactivity of the ASR and TCR in drug-induced akathisia. Hyperactive ASRs and TCRs also confirm suprasegmental hypodopaminergic state in akathisia. Although we keep in mind the confounding effects due to concurrent antidopaminergic treatments and the small sample group, we speculate that hyperactive ASRs and TCRs might be related to deficient control by forebrain and limbic-mainly amygdala-network in patients with drug-induced akathisia.

Lower limb flexor reflex: Comparisons between drug-induced akathisia and restless legs syndrome.

BACKGROUND AND OBJECTIVE: Akathisia is characterized by restlessness and crawling sensations similar to restless legs syndrome (RLS). Long latency flexor reflex (LLFR) which has helped to advance RLS pathophysiology has never been investigated in akathisia. Due to the clinical commonalities of akathisia and RLS, we investigated the behavior of LLFR in patients with akathisia aiming to understand pathophysiology of akathisia. PATIENTS AND METHODS: Seven patients with neuroleptic-induced akathisia, 12 drug-naïve patients with primary RLS and 17 healthy subjects were prospectively enrolled in the study. LLFR was recorded from unilateral tibialis anterior (TA) and long head of biceps femoris (BF) muscles after stimulating the sole by trains of electrical stimuli. We measured amplitude, latency, duration, presence of response and compared between three groups. RESULTS: One-way ANOVA showed mean durations of early and late responses recorded over TA were the longest in akathisia group compared to both RLS group and healthy subjects (p=0.012). The spatial spread of LLFR in akathisia patients was comparable to those of healthy subjects whereas presence of response on BF was significantly less in akathisia than RLS group. CONCLUSIONS: Our findings indicate increased excitability of LLFR pathway in akathisia group. These findings are probably due to lack of inhibition originated in regions other than those known to downregulate in RLS.

GC and VDR SNPs and Vitamin D Levels in Parkinson's Disease: The Relevance to Clinical Features.

Vitamin D deficiency is suggested to be associated with Parkinson's disease (PD). Our aim was to investigate the serum 25-hydroxyvitamin D3 (25OHD) levels of PD patients in Turkish cohort, to investigate any association of vitamin D binding protein (GC) genotypes with PD due to the significant role of GC in vitamin D transport, to determine whether vitamin D receptor (VDR) haplotype that we previously demonstrated to be a risk haplotype for AD is also a common haplotype for PD and to investigate any relevant consequence of serum 25OHD levels, GC or VDR genotypes on clinical features of PD. Three hundred eighty-two PD patients and 242 healthy subjects were included in this study. The serum 25OHD levels were investigated by CLIA, and GC and VDR SNPs were evaluated with LightSnip. Our results indicated a strong relationship between low serum 25OHD levels and PD (p < 0.001). rs7041 of GC and ApaI of VDR were associated with the PD risk (p < 0.05). Minor allele carriers for BsmI of VDR gene in both PD patients and healthy subjects had significantly higher levels of serum 25OHD (p < 0.05). The homozygous major allele carriers for rs2282679, rs3755967 and rs2298850 of GC gene in PD patients with slower progression had significantly higher levels of serum 25OHD (p  < 0.05). Minor allele carriers for FokI of VDR gene were more frequent in patients with advanced-stage PD (p < 0.05). Consequently, this is the first study demonstrating GC gene as a risk factor for PD. The relationship between PD's clinical features and low 25OHD or risk genotypes might have effects on PD independently.