The LRRK2 Arg1628Pro variant is a risk factor for Parkinson’s disease in the Chinese population

The c.G4883C variant in the leucine-rich repeat kinase 2 (LRRK2) gene (protein effect: Arg1628Pro) has been recently proposed as a second risk factor for sporadic Parkinson’s disease in the Han Chinese population (after the Gly2385Arg variant). In this paper, we analyze the Arg1628Pro variant and the associated haplotype in a large sample of 1,337 Han subjects (834 patients and 543 controls) ascertained from a single referral center in Taiwan. In our sample, the Arg1628Pro allele was more frequent among patients (3.8%) than among controls (1.8%; p = 0.004, OR 2.13, 95% CI 1.29–3.52). Sixty heterozygous and two homozygous carriers of the Arg1628Pro variant were identified among the patients, of which only one was also a carrier of the LRRK2 Gly2385Arg variant. We also show that carriers of the Arg1628Pro variant share a common, extended haplotype, suggesting a founder effect. Parkinson’s disease onset age was similar in patients who carried the Arg1628Pro variant and in those who did not carry it. Our data support the contention that the Arg1628Pro variant is a second risk factor for Parkinson’s disease in the Han Chinese population. Adding the estimated effects of Arg1628Pro (population attributable risk [PAR] ~4%) and Gly2385Arg variants (PAR ~6%) yields a total PAR of ~10%.     

Analysis of the LRRK2 Gly2385Arg variant in primary dystonia and multiple system atrophy in Taiwan

The c.G7153A variant in the LRRK2 gene (protein effect: Gly2385Arg) is emerging as an important risk factor for Parkinson's disease (PD) in the Han Chinese and Japanese populations. The prevalence of this variant in other neurodegenerative diseases and movement disorders remains almost completely unexplored. Using MALDI-TOF, we studied the Gly2385Arg variant in a large cohort of patients with primary dystonia (n=335) and a smaller series of patients with clinically diagnosed multiple system atrophy (MSA, n=57). The Gly2385Arg variant was identified in heterozygous state in 14 patients with primary dystonia (4.18%) and in three patients with MSA (5.26%). These frequencies do not differ statistically from that reported previously by us in Taiwanese controls (5%). We conclude that the Gly2385Arg variant is not associated with primary dystonia in Taiwan, supporting the specificity of the association between this variant and PD. Whether the Gly2385Arg variant modifies the risk for MSA deserves further study in larger samples.     

Analysis of the LRRK2 Gly2385Arg variant in Alzheimer's disease in Taiwan

ObjectiveTo analyze the Gly2385Arg (G2385R) mutation in Taiwanese Alzheimer's disease (AD) patients.BackgroundThe leucine-rich repeat kinase 2 (LRRK2) gene is well known to predispose subjects to Parkinson's disease (PD). The Gly2385Arg (G2385R) variant of LRRK2 is believed to be “East Asian”-specific, particularly in the Han Chinese population; however, whether the LRRK2 G2385R is associated with a risk of AD in pure Han-Chinese patients has not often been studied.MethodsA total of 209 AD patients (87 men, 122 women) and 180 age- and gender-matched controls were recruited and the demographic data of the AD patients were analyzed. Genotyping of the Gly2385Arg variant was studied using matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry.ResultsSubjects with the Gly2385Arg variant were all heterozygous carriers. The frequency of Gly2385Arg carriers did not differ significantly between the AD patients and controls (4.78% versus 4.44%, odds ratio = 1.04, 95% CI = 0.62–1.77, P = 0.87). In the AD patient group, the age of symptom onset, the length of education, or the MMSE score showed no significant differences between wild-type carriers and heterozygous variant carriers (P = 0.51, 0.43, and 0.09).ConclusionThe Gly2385Arg variant of LRRK2 may not be a major risk factor for AD in pure Han Chinese patient. Among the AD patients, Gly2385Arg carriers were not clinically different from wild-type carriers.     

Essential tremor and the common LRRK2 G2385R variant

Co-existence of Parkinson's disease (PD) and essential tremor (ET) suggests a possible overlapping pathophysiology between these two conditions. PD patients with leucine-rich repeat kinase-2 (LRRK2) mutations have been reported to present initially with ET. A common LRRK2 Gly2385Arg variant has been widely shown to be associated with a two fold increased risk of PD in various Asian populations. We analyzed the Gly2385Arg variant in a cohort of ET and controls. A total of 419 subjects comprising of 172 ET and 247 controls were included. The mean age, age at onset of ET, and age of controls were 52.1+/-19.6, 41.8+/-21.6, and 62.2+/-11.6 years, comprising of 53.0% and 54.3% men, respectively. The Gly2385Arg variant was demonstrated in 5/172 (2.9%) ET patients compared to 10/247 (4.0%) of controls (odds ratio=0.72, 95% CI 0.24, 2.1, p=0.6). All the Gly2385Arg carriers were heterozygotes. The LRRK2 Gly2385Arg variant is not a significant risk factor for ET in our population.     

Analysis of LRRK2 Gly2385Arg genetic variant in non-Chinese Asians.

A common LRRK2 missense variant, Gly2385Arg, has been found to be a genetic risk factor for Parkinson's disease (PD) in ethnic Chinese and Japanese. However, the presence of the variant in other non-Chinese Asian patients has not been fully clarified. We performed genetic analysis of the Gly2385Arg variant in 472 non-Chinese Asian subjects in Singapore (comprising of 166 PD and 306 controls of Malay/Indian ethnicity). The frequency of the heterozygous Gly2385Arg genotype was not significantly different in PD compared with controls (1.2% vs. 0.8%, odds ratio = 2.83, 95% CI 0.40, 20.2, P = 0.3). No subjects carried the homozygous genotype. Stratification by Malay and Indian ethnicity revealed that there were two carriers each among 98 (2.0%) Malay PD and 173 (1.2%) Malay controls (odds ratio = 1.78, 95% CI 0.25, 12.8, P = 0.6), but there were no carriers among 66 Indian PD and 133 Indian controls. We demonstrated that the Gly2385Arg variant could be detected in our Malay subjects. However, its frequency was much lower than the 8 to 10% prevalence previously reported in our Singaporean and Taiwanese Chinese PD population. The relevance of Gly2385Arg as a genetic risk factor may be restricted to selected Asian races, and more studies will be needed to confirm our observations.     

LRRK2 Gly2385Arg mutation and clinical features in a Chinese population with early-onset Parkinson’s disease compared to late-onset patients

The frequency of LRRK2 Gly2385Arg mutation in Hong Kong Chinese with early-onset (age 50 years) and controls. The mutation prevalence were 8.8, 8.3, and 0% for early-onset, late-onset, and controls, respectively. The mean age of onset among LRRK2 G2385R carriers was 42.7 years old for early-onset compared to 74.3 for late-onset patients. LRRK2 G2385R mutation appears to be as prevalent among early-onset as late-onset patients.     

常染色体显性遗传性帕金森病家系临床特征及LRRK2基因分析

目的 研究常染色体显性遗传家族性帕金森病(PD)患者的临床特征及其LRRK2基因突变.方法 对16例常染色体显性遗传家族史的PD患者LRRK2基因的外显子5、13、31、32、35、37、41、48进行测序检测.利用限制性片段长度多态性(RFLP)分析所发现的新突变c.1432 G＞TAsp478Tyr在240例散发性PD患者及214名健康者中的发生频率.结果 常染色体显性遗传家系PD患者与散发性PD患者比较临床特点以晚发为主,首发症状以静止性震颤(9例,56.25%,t=0.558,P=0.679)和动作迟缓(9例,56.25%,t=0.369,P=0.454)最为常见,其次是肌强直(6例,37.50%,t=1.324,P=0.735)和姿势障碍(5例,31.25%,t=2.369,P=0.956),对左旋多巴治疗反应良好,左旋多巴诱导的异动症少见.LRRK2基因突变检测发现6个突变:c.457 T＞C Leu153Leu、c.1432 G＞T Asp478Tyr、c.5457 T＞C Gly1819Gly、c.7153 G＞A Gly2385Arg、IVS31+28 T＞G、IVS37+162 T＞C.其中,c.1432 G＞T Asp478Tyr是未报道过的新突变.在240例散发性PD患者及214名健康者中均未发现有此突变.未发现与PD相关的LRRK2基因突变Arg1441Cys/Gly/His、Arg1514Gln、Tyr1699Cys、Ile2012Thr、Gly2019Ser和Ile2020Thr.结论 常染色体显性遗传性PD患者临床特征表现为典型的PD临床特征,存在LRRK2基因Asp478Tyr和Gly2385Arg突变.Asp478Tyr是未报道过的新突变.     

LRRK2 G2385R variant carriers of female Parkinson’s disease are more susceptible to motor fluctuation

The relation between the LRRK2 mutation and its effect on Parkinson’s disease (PD) has always caught a lot attention. Recent studies found that the G2385R polymorphism of LRRK2 may increase the risk of PD in Asian populations. Here we tried to clarify the relationship between the LRRK2 G2385R variant and the clinical profiles including motor complication in Chinese PD patients. We identified the LRRK2 variant in the Chinese Han population in northern China and evaluated the relationship between the G2385R variant and clinical profiles through comparison between 36 carriers and 139 non-carriers. We found that G2385R carriers scored significantly higher in motor fluctuation and dyskinesia than non-carriers. Logistic regression analysis showed that the G2385R variant was an independent risk factor for motor fluctuation in females (odds ratio = 12.538, 95 % CI 2.216–70.942, P = 0.004), and a Chi-squared test showed that the frequency of dyskinesia tended to be higher in the carrier group compared to the non-carrier group (16 vs. 4.4 %, P = 0.050, OR = 4.127, 95 % CI 1.074–15.864). These findings indicate that the variant was closely related to the occurrence of motor complication. Additionally, the G2385R variant was significantly related to the early-onset of PD in female carriers (20.0 vs. 1.5 %, odds ratio = 16.25, 95 % CI 1.557–169.618, P = 0.020). Our study found that the G2385R variant was significantly associated with motor complications and that this variant was an independent risk factor for motor fluctuation in females. These findings provide the necessary preliminary data to better understand the unique profile of PD G2385R variant carriers.     

A common missense variant in the LRRK2 gene, Gly2385Arg, associated with Parkinson’s disease risk in Taiwan

Mutations in the LRRK2 gene are a cause of autosomal dominant Parkinson’s disease (PD). Whether LRRK2 variants influence susceptibility to the commoner, sporadic forms of PD remains largely unknown. Data are particularly limited concerning the Asian population. In search for novel, biologically relevant variants, we sequenced the LRRK2 coding region in Taiwanese patients with PD. Four newly identified variants and another variant recently found in a Taiwanese PD family were tested for association with the disease in a sample of 608 PD cases and 373 ethnically matched controls. Heterozygosity for the Gly2385Arg variant was significantly more frequent among PD patients than controls (nominal p value=0.004, corrected for multiple comparisons=0.012, gender- and age-adjusted odds ratio=2.24, 95% C.I.: 1.29–3.88); this variant was uniformly distributed across genders and age strata. Two novel variants, Met1869Val and Glu1874Stop, were found in one PD case each; their pathogenic role remains, therefore, uncertain. The remaining two novel variants (Ala419Val and Pro755Leu) were present with similar frequency in cases and controls, and were therefore, interpreted as disease-unrelated polymorphisms. Our findings suggest that the LRRK2 Gly2385Arg is the first identified, functionally relevant variant, which acts as common risk factor for sporadic PD in the population of Chinese ethnicity.     

Olfactory Dysfunction in Parkinson's Disease Patients with the LRRK2 G2385R Variant

Olfactory dysfunction has been reported in Parkinson's disease(PD) patients carrying the LRRK2G2019 S variant in Caucasians but rarely in those with die LRRK2 G2385 R variant.In this study,we performed genotyping for the LRRK2 G2385 R variant in PD patients recruited from the Movement Disorder Clinic of Xuanwu Hospital in Beijing and in healthy controls randomly selected from the Beijing Longitudinal Study on Aging cohort.The "five-odor olfactory detection array",an olfactory threshold test,was used to assess olfactory function.One hundred and eighty-six participants were enrolled,comprising 43 PD patients without(iPD) and 25with(LRRK2-PD) the LRRK2 G2385 R variant,and 118 healthy controls.Our results showed mat the threshold of olfactory identification was significantly worse in PD patients than in controls,but not significantly different between me iPD and LRRK2-PD groups.These findings suggested that although olfactory function in LRRK2-PD patients is impaired,it is similar to that in iPD patients.     

LRRK2 mutations and Parkinson's disease in Sardinia--A Mediterranean genetic isolate

The Leucine-Rich Repeat Kinase 2 (LRRK2) Gly2019Ser mutation is frequent among Parkinson's disease (PD) patients from the Arab, Jewish, and Iberian populations, while another mutation, Arg1441Gly, is common in the Basque population. We studied the prevalence of these mutations in Sardinia, a Mediterranean genetic isolate with peculiar structure and similarities with the Basque population. Among 98 Sardinian PD probands we detected one heterozygous Gly2019Ser carrier. This mutation was also found in one of 55 Sardinian controls, an 85-year-old man, later shown to have a positive family history of parkinsonism. No carriers of Arg1441Gly, Arg1441Cys, or Arg1441His mutations were found among cases and controls. Our results suggest that the "Basque"LRRK2 mutation is absent or very rare in Sardinia. The Gly2019Ser mutation is present but its frequency is lower than that in Iberian, Arab, or Jewish populations. The identification of an 85-year-old, healthy Gly2019Ser carrier supports the concept that this mutation displays incomplete penetrance.     

LRRK2 Gly2385Arg variant is a risk factor of Parkinson's disease among Han-Chinese from mainland China

Mutations in the gene encoding Leucine-rich repeat kinase 2 (LRRK2) have been recently linked with autosomal-dominant parkinsonism, and polymorphisms have been commonly associated with sporadic Parkinson's disease (PD). A p.2385G>R variant has been reported as a risk factor for PD in Taiwan, Singapore and Japan. Herein, we have assessed the frequency of this polymorphism among the ethnic Han-Chinese population in a case–control study. A total of 600 patients with PD and 334 unrelated healthy controls were genotyped using PCR-restriction fragment length polymorphism analysis. Hardy–Weinberg equilibrium of each group was calculated, and differences in genotype frequencies between groups were assessed by the Chi-square test. In the PD cohort, 70 patients (11.7%) were heterozygous and 1 (0.2%) was homozygous for the p.2385G>R variant. This was significantly more frequent than in the controls [3.3%, Odds ratio = 3.9, 95% confidence interval (CI) = 2.1–7.5, P <  0.01]. Clinically, the age of PD onset of the p.2385G>R carriers was lower than the non-carriers ( P =  0.01). Our study indicates that this LRRK2 p.2385G>R substitution contributes to the development of PD in ethnic Han-Chinese population, which may play important implications for future study on molecular genetics and pathogenesis of PD.     

Is the G2019S LRRK2 mutation common in all southern European populations?

Mutations in the leucine-rich repeat kinase 2 (LRRK2) gene, especially the G2019S mutation, have been identified as a common cause of Parkinson's disease in southern European and other Mediterranean populations (Iberians, Ashkenazi Jews and North African Arabs). Owing to the geographic and historic vicinity of Greece with areas of high prevalence of LRRK2 mutations we studied the frequency of the G2019S mutation in a well characterized cohort of familial and sporadic Parkinson's disease patients of Greek origin from mainland Greece. The prevalence of the LRRK2 R1441C mutation and the G2385R Asian polymorphism was also determined. We identified no patients with any of the studied mutations/polymorphisms. Very low prevalence of the LRRK2 G2019S mutation has been reported in other southern European populations. LRRK2 mutations appear to be limited in certain populations and differing ancestry and founder effects may explain the reported variability. Accurate estimations of the frequency and penetrance of different LRRK2 mutations are essential for correct and cost-efficient use of genetic testing and proper genetic counseling of patients with Parkinson's disease.     

LRRK2 Gly2019Ser penetrance in Arab-Berber patients from Tunisia: a case-control genetic study

BACKGROUND: Several genes have been implicated in the pathogenesis of Parkinson's disease (PD). The aim of this study was to define the clinical symptoms and age-associated cumulative incidence of the most frequent mutation associated with PD, LRRK2 Gly2019Ser. METHODS: 238 patients with sporadic PD and 371 unrelated control participants from the Arab-Berber population were screened at the Institut National de Neurologie, Tunis. Symptoms of PD were assessed using the Hoehn and Yahr scale, the unified Parkinson's disease rating scale, and the Epworth scale. Genotyping for LRRK2 6055G-->A, which causes the Gly2019Ser mutation, was done in all participants, and the age-specific cumulative incidence of PD was calculated by Kaplan-Meier analysis. FINDINGS: 30% of patients with PD in this case-control sample were carriers of LRRK2 Gly2019Ser. The age of onset of symptoms and the clinical presentation of patients with LRRK2 Gly2019Ser were similar to those of patients with idiopathic PD. Carriers of LRRK2 Gly2019Ser were 22.6 times (95% CI 10.2-50.1) more likely to be affected by PD than non-carriers. Tremor was the predominant symptom in LRRK2 Gly2019Ser carriers (92% [homozygotes] vs 75% [heterozygotes] vs 69% [non-carriers]; Cochran-Armitage trend test p=0.0587). Disease severity, response to treatment, and disease duration were similar among LRRK2 Gly2019Ser homozygotes, heterozygotes, and non-carriers (p=0.85). Disease penetrance in LRRK2 Gly2019Ser carriers ranged from less than 20% in those younger than 50 years to greater than 80% at 70 years. INTERPRETATION: The LRRK2 Gly2019Ser mutation in patients with PD is a useful aid to diagnosis. LRRK2 Gly2019Ser penetrance can vary but in most carriers PD seems an inevitable consequence of ageing. LRRK2 Gly2019Ser considerably increases susceptibility to neuronal degeneration, although the process might be mediated by many triggers. By contrast, idiopathic PD is rare before 50 years and the prevalence only increases to 4% in the oldest members of the population. FUNDING: GlaxoSmithKline; National Institutes of Health; and Mayo Foundation.     

The LRRK2 G2385R variant is a risk factor for sporadic Parkinson's disease in the Korean population

The G2385R (SNP accession no. rs34778348) and R1628P (rs33949390) variants of leucine-rich repeat kinase 2 (LRRK2, PARK8) are emerging as an important risk factor for Parkinson's disease (PD) in the ethnic Chinese and Japanese populations. The purpose of this study was to investigate whether these variants are a genetic risk factor in sporadic PD patients in the Korean population. A total of 923 patients and 422 healthy subjects were included. The variants were screened by a SNaPshot assay. The LRRK2 G2385R variant was detected in 82 PD patients (8.9%, two homozygous and 80 heterozygous) and in 21 normal controls (5.0%, all heterozygous). The frequency of the LRRK2 G2385R variant in PD was significantly higher than in normal controls (adjusted odds ratio 1.83, p = 0.0170, 95% confidence interval 1.11–3.00). There were no differences in the mean age at onset or gender between the G2385R carriers and the non-carriers in PD patients. The LRRK2 R1628P variant was very rare (0.78% in patients versus 0.26% in controls) in the tested 384 patient–control pairs, and was not a significant risk factor. This study supports that the LRRK2 G2385R variant may be a genetic risk factor for sporadic PD in the Korean population.     

Lack of association between LRRK2 G2385R and cognitive dysfunction in Korean patients with Parkinson’s disease

Aside from the glucocerebrosidase gene, the genetic risk factors for cognitive decline in Parkinson’s disease (PD) are controversial. We investigated whether the G2385R polymorphism in leucine-rich repeat kinase 2 gene (LRRK2), a risk variant for the development of PD in East Asians, is associated with cognitive dysfunction in PD. We recruited 299 PD patients, consisting of 23 carriers and 276 non-carriers of LRRK2 G2385R, from 14 centers. Global cognitive function was assessed using the Mini-Mental State Examination (MMSE) or the Montreal Cognitive Assessment (MoCA). PD with cognitive dysfunction was defined as an MMSE Z score that, adjusting for age at study entry and years of education, was below -1.0 standard deviations.In multivariate analysis, PD duration, age at study entry and depression were significant risk factors for cognitive dysfunction as assessed by MMSE performance or the MoCA. In linear regression analysis of the association between MMSE Z scores and PD duration, there was no significant difference associated with the LRRK2 G2385R genotype. The interaction terms between PD duration and the LRRK2 G2385R genotype were not significant for the MMSE Z score but were significant for the MoCA. In conclusion, the LRRK2 G2385R genotype may not be associated with cognitive dysfunction in PD.     

Olfactory Dysfunction in Parkinson’s Disease Patients with the <Emphasis Type="Italic">LRRK2</Emphasis> G2385R Variant

Olfactory dysfunction has been reported in Parkinson’s disease (PD) patients carrying the LRRK2 G2019S variant in Caucasians but rarely in those with the LRRK2 G2385R variant. In this study, we performed genotyping for the LRRK2 G2385R variant in PD patients recruited from the Movement Disorder Clinic of Xuanwu Hospital in Beijing and in healthy controls randomly selected from the Beijing Longitudinal Study on Aging cohort. The “five-odor olfactory detection array”, an olfactory threshold test, was used to assess olfactory function. One hundred and eighty-six participants were enrolled, comprising 43 PD patients without (iPD) and 25 with (LRRK2-PD) the LRRK2 G2385R variant, and 118 healthy controls. Our results showed that the threshold of olfactory identification was significantly worse in PD patients than in controls, but not significantly different between the iPD and LRRK2-PD groups. These findings suggested that although olfactory function in LRRK2-PD patients is impaired, it is similar to that in iPD patients.     

Common variants of LRRK2 are not associated with sporadic Parkinson's disease

Multiple mutations in the gene for the leucine-rich repeat kinase (LRRK2) cause autosomal dominant late-onset parkinsonism (PARK8). The Gly2019Ser mutation appears to be common in different populations. To investigate whether this novel gene influences the non-Mendelian sporadic form of Parkinson's disease, we genotyped 121 single nucleotide polymorphisms comprehensively covering the entire LRRK2 gene region in a set of 340 Parkinson's disease patients and 680 matched control subjects from Germany. No association could be demonstrated. We have therefore no evidence for the existence of a common variant in LRRK2 that has a strong influence on Parkinson's disease risk.     

Analysis of Lrrk2 R1628P as a risk factor for Parkinson's disease

Common genetic variants that increase the risk for Parkinson's disease may differentiate patient subgroups and influence future individualized therapeutic strategies. Herein we show evidence for leucine-rich repeat kinase 2 (LRRK2) c.4883G>C (R1628P) as a risk factor in ethnic Chinese populations. A study of 1,986 individuals from 3 independent centers in Taiwan and Singapore demonstrates that Lrrk2 R1628P increases risk for Parkinson's disease (odds ratio, 1.84; 95% confidence interval, 1.20-2.83; p = 0.006). Haplotype analysis suggests an ancestral founder for carriers approximately 2,500 years ago. These findings support the importance of LRRK2 variants in sporadic Parkinson's disease. Ann Neurol 2008.     

Clinical and brain imaging characteristics in leucine-rich repeat kinase 2-associated PD and asymptomatic mutation carriers

The objective of this research was to evaluate a possible endophenotype in leucine-rich repeat kinase 2 (LRRK2)-associated Parkinson's disease (PD). Ten symptomatic LRRK2 patients, 24 sporadic Parkinson's disease patients as well as 10 asymptomatic LRRK2 mutation carriers and 29 matched healthy controls underwent comprehensive clinical assessments with respect to motor and non-motor symptoms. Transcranial sonography and magnetic resonance imaging (voxel-based morphometry [VBM]) were assessed to evaluate morphological imaging characteristics. LRRK2 patients had an earlier onset of motor symptoms and a more benign phenotype of motor and non-motor characteristics compared to sporadic Parkinson's disease patients. However, depression scores were higher in LRRK2 patients. No clinical differences were found regarding motor and non-motor symptoms in asymptomatic LRRK2 mutation carriers in comparison to controls. Transcranial sonography showed hyperechogenicity of the substantia nigra in both patients' cohorts as well as in asymptomatic LRRK2 mutation carriers. Voxel-based morphometry revealed increased gray matter volume of the cerebellum and precentral gyrus in LRRK2 patients and of the cuneus in asymptomatic LRRK2 mutation carriers. In contrast, we found decreased basal ganglia gray matter volume in LRRK2 patients compared to controls. Increased gray matter volume of different anatomical structures associated with motor loops in LRRK2 patients and asymptomatic LRRK2 mutation carriers compared to age-matched sporadic Parkinson's disease patients and controls might indicate compensatory mechanism in LRRK2 mutation carriers due to motor network plasticity not only in the symptomatic stage of the disease but even in the premotor phase. Substantia nigra hyperechogenicity in yet unaffected LRRK2 mutation carriers indicates morphologic alterations in an asymptomatic stage of disease.