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Figure.
Compound heterozygous mutations in the parkin gene compared with control subjects. Patient 65 had deletions of exons 2 and 7, patient 3 had a duplication of exon 11 and a deletion of exon 2, and patient 18 had deletions of exons 3 and 7. Solid arrows indicate deletions; open arrow, duplication.

Compound heterozygous mutations in the parkin gene compared with control subjects. Patient 65 had deletions of exons 2 and 7, patient 3 had a duplication of exon 11 and a deletion of exon 2, and patient 18 had deletions of exons 3 and 7. Solid arrows indicate deletions; open arrow, duplication.

Table 1. 
Clinical Features and Their Correlation With Age at Onset in 94 Patients With EOPD
Clinical Features and Their Correlation With Age at Onset in 94 Patients With EOPD
Table 2. 
Clinical Features Related to Levodopa Treatment and Their Correlation With Age at Onset in 65 Patients With EOPD
Clinical Features Related to Levodopa Treatment and Their Correlation With Age at Onset in 65 Patients With EOPD
Table 3. 
Comparison of Clinical Variables Between the Younger Group and the Older Group*
Comparison of Clinical Variables Between the Younger Group and the Older Group*
Table 4. 
Demographic and Clinical Features of the 3 Patients With Parkin Gene Mutations
Demographic and Clinical Features of the 3 Patients With Parkin Gene Mutations
1.
Quinn  NCritchley  PMarsden  CD Young onset Parkinson's disease. Mov Disord 1987;273- 91
PubMedArticle
2.
Marder  KLevy  GLouis  ED  et al.  Familial aggregation of early- and late-onset Parkinson's disease. Ann Neurol 2003;54507- 513
PubMedArticle
3.
Hedrich  KMarder  KHarris  J  et al.  Evaluation of 50 probands with early-onset Parkinson's disease for Parkin mutations. Neurology 2002;581239- 1246
PubMedArticle
4.
Gibb  WRLees  AJ A comparison of clinical and pathological features of young- and old-onset Parkinson's disease. Neurology 1988;381402- 1406
PubMedArticle
5.
Giovannini  PPiccolo  IGenitrini  S  et al.  Early-onset Parkinson's disease. Mov Disord 1991;636- 42
PubMedArticle
6.
Pederzoli  MGirotti  FScigliano  GAiello  GCarella  FCaraceni  T L-dopa long-term treatment in Parkinson's disease: age-related side effects. Neurology 1983;331518- 1522
PubMedArticle
7.
Tanner  CMOttman  RGoldman  SM  et al.  Parkinson disease in twins: an etiologic study. JAMA 1999;281341- 346
PubMedArticle
8.
Polymeropoulos  MHLavedan  CLeroy  E  et al.  Mutation in the α-synuclein gene identified in families with Parkinson's disease. Science 1997;2762045- 2047
PubMedArticle
9.
Kitada  TAsakawa  SHattori  N  et al.  Mutations in the parkin gene cause autosomal recessive juvenile parkinsonism. Nature 1998;392605- 608
PubMedArticle
10.
Wintermeyer  PKruger  RKuhn  W  et al.  Mutation analysis and association studies of the UCHL1 gene in German Parkinson's disease patients. Neuroreport 2000;112079- 2082
PubMedArticle
11.
Valente  EMBentivoglio  ARDixon  PH  et al.  Localization of a novel locus for autosomal recessive early-onset parkinsonism, PARK6, on human chromosome 1p35-p36. Am J Hum Genet 2001;68895- 900
PubMedArticle
12.
Bonifati  VRizzu  Pvan Baren  MJ  et al.  Mutations in the DJ-1 gene associated with autosomal recessive early-onset parkinsonism. Science 2003;299256- 259
PubMedArticle
13.
Funayama  MHasegawa  KKowa  HSaito  MTsuji  SObata  F A new locus for Parkinson's disease (PARK8) maps to chromosome 12p11.2-q13.1. Ann Neurol 2002;51296- 301
PubMedArticle
14.
Abbas  NLucking  CBRicard  S  et al. French Parkinson's Disease Genetics Study Group and the European Consortium on Genetic Susceptibility in Parkinson's Disease, A wide variety of mutations in the parkin gene are responsible for autosomal recessive parkinsonism in Europe. Hum Mol Genet 1999;8567- 574
PubMedArticle
15.
Kann  MJacobs  HMohrmann  K  et al.  Role of parkin mutations in 111 community-based patients with early-onset parkinsonism. Ann Neurol 2002;51621- 625
PubMedArticle
16.
Lucking  CBDurr  ABonifati  V  et al. French Parkinson's Disease Genetics Study Group, Association between early-onset Parkinson's disease and mutations in the parkin gene. N Engl J Med 2000;3421560- 1567
PubMedArticle
17.
Schouten  JPMcElgunn  CJWaaijer  RZwijnenburg  DDiepvens  FPals  G Relative quantification of 40 nucleic acid sequences by multiplex ligation-dependent probe amplification. Nucleic Acids Res 2002;30e57
PubMedArticle
18.
Sellner  LNTaylor  GR MLPA and MAPH: new techniques for detection of gene deletions. Hum Mutat 2004;23413- 419
PubMedArticle
19.
Gelb  DJOliver  EGilman  S Diagnostic criteria for Parkinson disease. Arch Neurol 1999;5633- 39
PubMedArticle
20.
Kang  YWNa  DLHahn  S The validity study on the Korean Mini-Mental State Examination (K-MMSE) in dementia patients. J Korean Neurol Assoc 1997;15300- 307
21.
Zetusky  WJJankovic  JPirozzolo  FJ The heterogeneity of Parkinson's disease: clinical and prognostic implications. Neurology 1985;35522- 526
PubMedArticle
22.
Muthane  UBSwamy  HSSatishchandra  PSubhash  MNRao  SSubbakrishna  D Early onset Parkinson's disease: are juvenile- and young-onset different? Mov Disord 1994;9539- 544
PubMedArticle
23.
Kidron  DMelamed  E Forms of dystonia in patients with Parkinson's disease. Neurology 1987;371009- 1011
PubMedArticle
24.
Paviour  DCSurtees  RALees  AJ Diagnostic considerations in juvenile parkinsonism. Mov Disord 2004;19123- 135
PubMedArticle
Original Contribution
August 2006

Clinical Features and Gene Analysis in Korean Patients With Early-Onset Parkinson Disease

Author Affiliations

Author Affiliations: Departments of Neurology (Drs Chung, Lee, and J.-Y. Kim) and Laboratory Medicine (Drs Ki and I.-S. Kim), Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.

Arch Neurol. 2006;63(8):1170-1174. doi:10.1001/archneur.63.8.1170
Abstract

Background  Systematic analysis of clinical features and gene mutations has not been performed in Korean patients with early-onset Parkinson disease (PD).

Objective  To investigate the clinical characteristics and genetic background of Korean patients with early-onset PD.

Design  Clinical and genetic study.

Setting  University hospital.

Patients  Ninety-four patients with early-onset PD (mean ± SD age at onset, 39.8 ± 7.3 years) of 1100 patients with PD.

Interventions  Analysis of clinical characteristics and mutation analysis of the parkin and PTEN-induced kinase (PINK1) genes by direct sequencing and gene-dosage analysis using the multiplex ligation–dependent probe amplification technique.

Main Outcome Measures  The correlation between age at onset and clinical characteristics and the clinical features of patients with onset before age 30 years vs patients with onset after age 30 years.

Results  Because age at onset was younger, levodopa-induced dyskinesia and off-dystonia were more frequently observed (P=.008). Patients affected before age 30 years showed more frequent levodopa-induced dyskinesia and off-dystonia (P=.002). We identified 3 patients (5%) with parkin gene mutations but none with the PINK1 mutation.

Conclusions  Earlier onset of levodopa-induced dyskinesia and off-dystonia were characteristic features of early-onset PD, especially before an onset age of 30 years. However, parkin gene mutations were less frequent in these patients than in Japanese groups reported elsewhere.

Although Parkinson disease (PD) is a common age-related neurodegenerative disorder, it also can manifest earlier in life. When parkinsonism presents before age 40 to 50 years, it is referred to as early-onset PD (EOPD).13 Patients with EOPD have been known to have a more benign course, to rarely have dementia, to respond better to levodopa therapy, but to develop more severe levodopa-induced dyskinesia (LID) and motor fluctuations.46

Despite the uncertain etiology of most PD, a previous study7 suggested that genetic factors play a more important role in the pathogenesis of EOPD than in older-onset PD. To date, more than 10 genetic loci and 6 genes (α-synuclein, parkin, ubiquitin carboxy-terminal hydrolase L1, PTEN-induced kinase [PINK1], Parkinson disease [autosomal recessive, early onset] 7, and leucine-rich repeat kinase 2) have been linked to PD.813 Among these, the mutations in the parkin genes have been frequently documented in patients with EOPD worldwide.3,1416

Because there are, to our knowledge, no systematic studies of the clinical features and gene mutations in Korean patients with EOPD, we investigated the clinical characteristics and gene mutations in the parkin and PINK1 genes of patients with EOPD in Korea. For mutation analysis of the parkin gene, we introduced gene-dosage analysis using the recently developed multiplex ligation–dependent probe amplification technique,17 which has proved to be a reliable tool for the diagnosis of genetic diseases characterized by large gene deletions or duplications.18

METHODS
PATIENTS

Early-onset PD was defined as PD beginning before age 50 years. We enrolled 94 patients with EOPD (8.5%; 55 men and 39 women; mean ± SD age at onset, 39.8 ± 7.3 years) of 1100 patients with PD. The diagnosis of PD was based on the National Institute of Neurological Disorders and Stroke diagnostic criteria.19 Patients were excluded if they had a history of encephalitis, repeated strokes, head trauma, or treatment with neuroleptics or if they had atypical features other than the known phenotypes associated with the parkin mutation, such as dystonia and hyperreflexia.

CLINICAL ANALYSIS

We performed a detailed clinical study that included age at onset, disease duration, presence of family history, first presenting symptoms, presence of dystonia before treatment, and dysautonomic symptoms. For cognitive assessment, we used the Korean version of the Mini-Mental State Examination with informed consent.20 The cutoff score for cognitive impairment was less than 25. We examined patient drug response: the presence of LID or off-dystonia. We analyzed the relationship between age at onset and the clinical characteristics. To compare differences in the clinical characteristics according to age at onset, we divided patients with EOPD into 2 groups: those younger than 30 years (younger group) and those older than 30 years (older group).

GENETIC ANALYSIS

With informed consent, screening for mutations in the parkin and PINK1 genes were performed in 55 of 94 patients with EOPD. Genomic DNA was extracted from peripheral blood leukocytes, and all coding exons and flanking introns of the parkin and PINK1 genes were amplified and sequenced. Multiplex ligation–dependent probe amplification was conducted according to the supplied protocol using a parkin probe kit (MRC-Holland, Amsterdam, the Netherlands). Using Genscan and Genotyper and a spreadsheet program (Microsoft Excel; Microsoft Corp, Redmond, Wash), peak areas of each fragment were compared with those of a control sample to obtain a dosage quotient representing the gene dosage of each amplicon. Detailed methods for data analysis can be found on the manufacturer's Web site (http://www.mrc-holland.com). Because a positive control was not included in the multiplex ligation–dependent probe amplification analysis, a real-time polymerase chain reaction method was used to confirm the deletion or duplication mutations identified in the present study.

STATISTICAL ANALYSIS

Correlation between age at onset and clinical variables was assessed using a Wilcoxon rank sum test, a Wilcoxon rank sum test with the Bonferroni correction, and Spearman correlation coefficients. To compare groups (younger vs older), Fisher exact and Wilcoxon rank sum tests were used. P<.05 was used as the criterion for statistical significance.

RESULTS
CLINICAL DATA

Mean ± SD age at onset was 39.8 ± 7.3 years, and mean ± SD disease duration of parkinsonism was 50.1 ± 43.8 months. Patients with an earlier age at onset had a longer disease duration (P<.001). Although tremor at rest (43%) was the most frequent initial symptom, followed by akinetic-rigid syndrome (33%), the frequency of initial symptoms did not correlate with age at onset (P>.99). Dystonia in the course of the disease before levodopa therapy negatively correlated with age at onset (P = .04). Dysautonomic symptoms did not correlate with age at onset. Of 56 patients who completed the Korean version of the Mini-Mental State Examination, the score was less than 25 in 7 patients (13%) in the younger group. Hoehn and Yahr stage at entry and Mini-Mental State Examination score did not correlate with age at onset. Clinical features and their correlation with age at onset in patients with EOPD are summarized in Table 1.

Sixty-five of 94 patients were treated with levodopa. Levodopa-induced dyskinesia and off-dystonia were observed in 21 (32%) and 30 (46%) of the levodopa-treated patients. The frequencies of LID (P=.008) and off-dystonia (P=.002) were negatively correlated with age at onset (Table 2).

Comparing the clinical characteristics between the younger group and the older group, disease duration was longer in the younger group. Both LID (P=.01) and off-dystonia (P=.02) were more frequently observed in the younger group. Treatment duration before developing off-dystonia was longer in the younger group than in the older group (P=.02). Other clinical characteristics evaluated were not significantly different in comparisons between the 2 groups (Table 3).

CLINICAL FEATURES OF PATIENTS WITH PARKIN GENE MUTATIONS

Mutations in the parkin gene were detected in 3 (5%) of 55 patients, but none had the PINK1 gene mutation. The 3 patients with parkin gene mutations (patients 3, 18, and 65) were compound heterozygous for Ex2del/Ex7del, Ex2del/Ex11dup, and Ex3del/Ex7del, respectively (Figure and Table 4). Parkin gene mutations were confirmed by means of a real-time polymerase chain reaction method. No patients with parkin gene mutations had a family history of parkinsonism, and mean ± SD age at onset was younger than that in patients without parkin gene mutations (22.7 ± 14.2 vs 39.9 ± 6.5 years). The clinical features of patients with the PARK2 gene mutation are summarized in Table 4. Patient 18 received agonist monotherapy (ropinirole hydrochloride, 6 mg/d) with good response. DNA samples from the parents of patient 65 were available for segregation analysis and revealed that the proband's parents carried 1 of the 2 deletion mutations.

COMMENT

In this study, the frequency of EOPD is consistent with that in previous studies5,21 of EOPD with onset before age 40 years. The observed initial symptoms in patients with EOPD, including the preponderance of akinetic-rigidity or resting tremor, is still controversial.4,22 In our patients with EOPD, resting tremor was the most frequent presenting symptom, although there was no correlation with age at onset.

In this study, despite the low frequency of dystonia as an initial symptom, the frequency of dystonia before levodopa treatment was 6.4%. Furthermore, off-dystonia occurred in up to 46.2% of patients. We found that the younger the age at onset, the more likely the presence of total dystonia, including off-dystonia. This finding is in agreement with previous studies.23

Corresponding with a previous study,4 these clinical data show that axial symptoms, such as gait disturbance, were of low frequency. Cognitive impairment was rarely observed in these patients with EOPD with longer disease duration. This finding is consistent with that of previous studies.5 These clinical data show a high frequency of autonomic dysfunction in EOPD, similar to those of Giovannini and colleagues.5 However, in contrast to a previous study,22 there was no correlation between autonomic dysfunction and age at onset.

Consistent with previous studies,1,4,5 this study confirmed that most patients with EOPD have a good response to levodopa therapy. We also found that LID and off-dystonia were more frequently identified in the younger-onset group. Because of the longer disease duration in the younger group, we assume that an increased incidence of LID and off-dystonia may result from not only early age at onset but also long disease duration.

As a result of the gene-dosage analysis, we found 3 patients who were compound heterozygous for parkin gene mutations. In the present study, parkin gene mutations were less frequent than reported in previous studies, and no mutation was found in the PINK1 gene.3,16,24 A possible explanation is that most of the patients with EOPD were sporadic cases. It is also possible that there might be an ethnic difference in the genetic background of EOPD.

The clinical phenotype of patients with parkin gene mutations was similar to that of patients without parkin gene mutations. Therefore, patients with parkin gene mutations could not be distinguished on the basis of clinical features and were distinguished from the whole patient population only by genetic testing.

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Article Information

Correspondence: Won Yong Lee, MD, PhD, Department of Neurology, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50, Ilwon-Dong, Kangnam-Gu, Seoul, 135-710, Korea (wylee@smc.samsung.co.kr).

Accepted for Publication: March 10, 2006.

Author Contributions: Drs Chung and Ki contributed equally to this work. Study concept and design: Lee. Acquisition of data: Chung, Ki, Lee, I.-S. Kim, and J.-Y. Kim. Analysis and interpretation of data: Chung, Ki, and Lee. Drafting of the manuscript: Chung, Ki, Lee, I.-S. Kim, and J.-Y. Kim. Critical revision of the manuscript for important intellectual content: Ki and Lee. Statistical analysis: Chung. Obtained funding: Chung, Ki, and Lee. Administrative, technical, and material support: Ki, I.-S. Kim, and J.-Y. Kim. Study supervision: Lee.

Funding/Support: This work was supported by a grant from the IN-SUNG Foundation for Medical Research (Dr Lee) and by grant SBRI C-A5-102-1 from the Samsung Biomedical Research Institute (Dr Ki).

References
1.
Quinn  NCritchley  PMarsden  CD Young onset Parkinson's disease. Mov Disord 1987;273- 91
PubMedArticle
2.
Marder  KLevy  GLouis  ED  et al.  Familial aggregation of early- and late-onset Parkinson's disease. Ann Neurol 2003;54507- 513
PubMedArticle
3.
Hedrich  KMarder  KHarris  J  et al.  Evaluation of 50 probands with early-onset Parkinson's disease for Parkin mutations. Neurology 2002;581239- 1246
PubMedArticle
4.
Gibb  WRLees  AJ A comparison of clinical and pathological features of young- and old-onset Parkinson's disease. Neurology 1988;381402- 1406
PubMedArticle
5.
Giovannini  PPiccolo  IGenitrini  S  et al.  Early-onset Parkinson's disease. Mov Disord 1991;636- 42
PubMedArticle
6.
Pederzoli  MGirotti  FScigliano  GAiello  GCarella  FCaraceni  T L-dopa long-term treatment in Parkinson's disease: age-related side effects. Neurology 1983;331518- 1522
PubMedArticle
7.
Tanner  CMOttman  RGoldman  SM  et al.  Parkinson disease in twins: an etiologic study. JAMA 1999;281341- 346
PubMedArticle
8.
Polymeropoulos  MHLavedan  CLeroy  E  et al.  Mutation in the α-synuclein gene identified in families with Parkinson's disease. Science 1997;2762045- 2047
PubMedArticle
9.
Kitada  TAsakawa  SHattori  N  et al.  Mutations in the parkin gene cause autosomal recessive juvenile parkinsonism. Nature 1998;392605- 608
PubMedArticle
10.
Wintermeyer  PKruger  RKuhn  W  et al.  Mutation analysis and association studies of the UCHL1 gene in German Parkinson's disease patients. Neuroreport 2000;112079- 2082
PubMedArticle
11.
Valente  EMBentivoglio  ARDixon  PH  et al.  Localization of a novel locus for autosomal recessive early-onset parkinsonism, PARK6, on human chromosome 1p35-p36. Am J Hum Genet 2001;68895- 900
PubMedArticle
12.
Bonifati  VRizzu  Pvan Baren  MJ  et al.  Mutations in the DJ-1 gene associated with autosomal recessive early-onset parkinsonism. Science 2003;299256- 259
PubMedArticle
13.
Funayama  MHasegawa  KKowa  HSaito  MTsuji  SObata  F A new locus for Parkinson's disease (PARK8) maps to chromosome 12p11.2-q13.1. Ann Neurol 2002;51296- 301
PubMedArticle
14.
Abbas  NLucking  CBRicard  S  et al. French Parkinson's Disease Genetics Study Group and the European Consortium on Genetic Susceptibility in Parkinson's Disease, A wide variety of mutations in the parkin gene are responsible for autosomal recessive parkinsonism in Europe. Hum Mol Genet 1999;8567- 574
PubMedArticle
15.
Kann  MJacobs  HMohrmann  K  et al.  Role of parkin mutations in 111 community-based patients with early-onset parkinsonism. Ann Neurol 2002;51621- 625
PubMedArticle
16.
Lucking  CBDurr  ABonifati  V  et al. French Parkinson's Disease Genetics Study Group, Association between early-onset Parkinson's disease and mutations in the parkin gene. N Engl J Med 2000;3421560- 1567
PubMedArticle
17.
Schouten  JPMcElgunn  CJWaaijer  RZwijnenburg  DDiepvens  FPals  G Relative quantification of 40 nucleic acid sequences by multiplex ligation-dependent probe amplification. Nucleic Acids Res 2002;30e57
PubMedArticle
18.
Sellner  LNTaylor  GR MLPA and MAPH: new techniques for detection of gene deletions. Hum Mutat 2004;23413- 419
PubMedArticle
19.
Gelb  DJOliver  EGilman  S Diagnostic criteria for Parkinson disease. Arch Neurol 1999;5633- 39
PubMedArticle
20.
Kang  YWNa  DLHahn  S The validity study on the Korean Mini-Mental State Examination (K-MMSE) in dementia patients. J Korean Neurol Assoc 1997;15300- 307
21.
Zetusky  WJJankovic  JPirozzolo  FJ The heterogeneity of Parkinson's disease: clinical and prognostic implications. Neurology 1985;35522- 526
PubMedArticle
22.
Muthane  UBSwamy  HSSatishchandra  PSubhash  MNRao  SSubbakrishna  D Early onset Parkinson's disease: are juvenile- and young-onset different? Mov Disord 1994;9539- 544
PubMedArticle
23.
Kidron  DMelamed  E Forms of dystonia in patients with Parkinson's disease. Neurology 1987;371009- 1011
PubMedArticle
24.
Paviour  DCSurtees  RALees  AJ Diagnostic considerations in juvenile parkinsonism. Mov Disord 2004;19123- 135
PubMedArticle
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