Current Status of Huntington's Disease in Korea: A Nationwide Survey and National Registry Analysis

Neurodegenerative Disorders: Mechanisms of Degeneration and Therapeutic Approaches with Their Clinical Relevance

Neurodegenerative disorders (NDs) are expected to pose a significant challenge for both medicine and public health in the upcoming years due to global demographic changes. NDs are mainly represented by degeneration/loss of neurons, which is primarily accountable for severe mental illness. This neuronal degeneration leads to many neuropsychiatric problems and permanent disability in an individual. Moreover, the tight junction of the brain, blood-brain barrier (BBB)has a protective feature, functioning as a biological barrier that can prevent medicines, toxins, and foreign substances from entering the brain. However, delivering any medicinal agent to the brain in NDs (i.e., Multiple sclerosis, Alzheimer's, Parkinson's, etc.) is enormously challenging. There are many approved therapies to address NDs, but most of them only help treat the associated manifestations. The available therapies have failed to control the progression of NDs due to certain factors, i.e., BBB   and drug-associated undesirable effects. NDs have extremely complex pathology, with many pathogenic mechanisms involved in the initiation and progression; thereby, a limited survival rate has been observed in ND patients. Hence, understanding the exact mechanism behind NDs is crucial to developing alternative approaches for improving ND patients' survival rates. Thus, the present review sheds light on different cellular mechanisms involved in NDs and novel therapeutic approaches with their clinical relevance, which will assist researchers in developing alternate strategies to address the limitations of conventional ND therapies. The current work offers the scope into the near future to improve the therapeutic approach of NDs.

Analysis of HTT CAG repeat expansion among healthy individuals and patients with chorea in Korea

BACKGROUND

Although the epidemiology of Huntington's disease (HD) in Korea differs notably from that in Western countries, the genetic disparities between these regions remain unclear.

OBJECTIVE

To investigate the characteristics and clinical significance of cytosine-adenine-guanine (CAG) repeat size associated with HD in the Korean population.

METHODS

We analyzed the CAG repeat lengths of the HTT gene in 941 healthy individuals (1,882 alleles) and 954 patients with chorea (1,908 alleles) from two referral hospitals in Korea. We presented normative CAG repeat length data for the Korean population and computed the reduced penetrance (36-39 CAG) and intermediate allele (27-35 CAG) frequencies in the two groups. Furthermore, we investigated the relationship between intermediate alleles and chorea development using logistic regression models in individuals aged ≥55 years.

RESULTS

The mean (±standard deviation) CAG repeat length in healthy individuals was 17.5 ± 2.0, with a reduced penetrance allele frequency of 0.05 % (1/1882) and intermediate allele frequency of 0.69 % (13/1882). We identified 213 patients with genetically confirmed HD whose CAG repeat length ranged from 39 to 140, with a mean of 45.2 ± 7.9 in the longer allele. Compared with normal CAG repeat alleles, intermediate CAG repeat alleles were significantly related to a higher risk of developing chorea (age of onset range, 63-84 years) in individuals aged ≥55 years.

CONCLUSIONS

This study provides insights into the specific characteristics of CAG repeat lengths in the HTT gene in the Korean population. The reduced penetrance and intermediate allele frequencies in the Korean general population seem to be lower than those reported in Western populations. The presence of intermediate alleles may increase the risk of chorea in the Korean elderly population, which requires further large-scale investigations.

Epidemiology of Chronic Inflammatory Demyelinating Polyneuropathy in South Korea: A Population-Based Study

BACKGROUND AND PURPOSE

We performed a population-based study to determine the prevalence and incidence of chronic inflammatory demyelinating polyneuropathy (CIDP) in South Korea using data from the Korean Health Insurance Review and Assessment Service (HIRA) database.

METHODS

Data recorded in the HIRA database between January 2016 and December 2020 were analyzed. The inclusion criteria in this study for patients with CIDP were a diagnostic code of G61.8 in the seventh and eighth revision of the Korean Standard Classification of Disease and a >3-month history of oral immunosuppressant use. The age-adjusted incidence rate and prevalence of CIDP in South Korea were also analyzed.

RESULTS

CIDP was newly diagnosed in 953 patients during the study period. The mean age at diagnosis was 58.36 years, and the male-to-female ratio was 1.74. The age-adjusted incidence rates were 0.22, 0.21, 0.23, 0.30, and 0.25 per 100,000 person-years in 2016, 2017, 2018, 2019, and 2020, respectively. The age-adjusted prevalence was estimated at 1.16 per 100,000 persons in 2020. Age and the Elixhauser Comorbidity Index were associated with the in-hospital mortality of patients with CIDP. Infection and cardiovascular disease (CVD) were also significantly associated with the in-hospital mortality of those patients. Acute-onset CIDP was initially diagnosed in an estimated 101 out of 953 patients with CIDP.

CONCLUSIONS

The prevalence and incidence rates of CIDP in South Korea were comparable between this nationwide cohort study and previous studies. Common comorbidities such as CVD and diabetes should be appropriately monitored in patients with CIDP to prevent a poor prognosis and socioeconomic burden.

Huntington's Disease in Chile: Epidemiological and Genetic Aspects

INTRODUCTION

Huntington's disease (HD) is a neurodegenerative, autosomal dominant disabling condition due to an expansion of the CAG trinucleotide in the HTT gene. Motor, psychiatric, and cognitive disorders characterize it. Chilean reports on HD in the era of molecular diagnosis were wanted.

METHODS

This is a retrospective analysis of a prospective cohort of patients with HD seen at the Center for Movement Disorders (CETRAM) in Chile between 2013 and 2019. Sociodemographic, genotype, and neuropsychiatric features were investigated.

RESULTS

One hundred three probands with HD were identified. The majority (63.1%) were born in the metropolitan region, followed by the VIII and V regions with 8.73% and 7.76%, respectively. When pedigrees were analyzed, ninety unrelated families encompassing 1,007 individuals were identified; among relatives, other 35 manifested HD, and 106 died of HD. Besides, five hundred seventy-nine individuals were at genetic risk. The minimum estimated prevalence of HD in Chile in 2019 was 0.72 × 100,000 inhabitants. The mean CAG repeats (CAGR) of 47.2 ± 10.74 for the expanded allele and 17.93 ± 2.05 for the normal allele. The mean age of onset was 41.39 ± 13.47 years. Juvenile cases represented 7.8% of this cohort, and 4.9% had a late onset. There was a negative correlation between the age of onset and the CAGR of the expanded allele (r =-0.84 p < 0.0001). Besides, 79.6% had a family history of HD.

CONCLUSIONS

This is the first report characterizing genetics, motor, and neuropsychiatric features in patients with HD in Chile. The mean length of CAGR expansion of the abnormal allele was similar to previous reports in North America (i.e., Mexico and Canada) and higher than that reported in the neighboring country of Argentina. According to previous estimations, the minimal prevalence of HD in Chile may be lower than expected.

Global Epidemiology of Movement Disorders: Rare or Underdiagnosed?

In this manuscript, we review the epidemiology of movement disorders including Parkinson's disease (PD), atypical parkinsonism, essential tremor, dystonia, functional movement disorders, tic disorders, chorea, and ataxias. We emphasize age-, sex-, and geography-based incidence and prevalence, as well as notable trends including the rising incidence and prevalence of PD. Given the growing global interest in refining clinical diagnostic skills in recognizing movement disorders, we highlight some key epidemiological findings that may be of interest to clinicians and health systems tasked with diagnosing and managing the health of patients with movement disorders.

Increased 10-Year Prevalence of Huntington's Disease in South Korea: An Analysis of Medical Expenditure Through the National Healthcare System

BACKGROUND AND PURPOSE

This study aimed to determine the updated 10-year prevalence of Huntington's disease (HD) in South Korea and the medical and economic burdens across the duration of the disease.

METHODS

Data from the National Health Insurance database during 2010-2019 were analyzed. We identified HD cases using predefined criteria. Information on age at diagnosis, sex, and common nonneurological comorbidities were collected. We analyzed individual patterns of the use of medical services and yearly medical expenditure. Incidence rates, 10-year prevalence rates, and longitudinal medical expenditure changes were assessed.

RESULTS

New patients with HD (average=152.10) were detected every year, with an annual incidence of 0.29 per 100,000. The estimated 10-year prevalence of HD was 2.2 per 100,000. The most common ages at the time of diagnosis were 50-59 years (23.3%). In 2019, 56.4% of patients with HD were followed-up at referral or general hospitals, and 32.2% were managed at long-term-care hospitals. The annual medical cost for an individual was KRW 6,569,341±895,097 (mean±SD) (mean≈USD 5,653). Medical expenditure was the highest in those aged 60-79 years, and lowest in those younger than 30 years. However, in all age groups, the annual medical expenditure was highest during the 9 years following a diagnosis.

CONCLUSIONS

This study found that the actual prevalence of HD in South Korea was higher than previously thought and that patients are in a situation with high medical expenditure that persists over time.

Prevalence and Incidence of Huntington's Disease: An Updated Systematic Review and Meta-Analysis

The incidence and prevalence of Huntington's disease (HD) based on a systematic review and meta-analysis of 20 studies published from 1985 to 2010 was estimated at 0.38 per 100,000 person-years (95% confidence interval [CI], 0.16-0.94) and 2.71 per 100,000 persons (95% CI, 1.55-4.72), respectively. Since 2010, there have been many new epidemiological studies of HD. We sought to update the global estimates of HD incidence and prevalence using data published up to February 2022 and perform additional analyses based on study continent. Medline and Embase were searched for epidemiological studies of HD published between 2010 and 2022. Risk of bias was assessed using a quality assessment tool. Estimated pooled prevalence or incidence was calculated using a random-effects meta-analysis. A total of 33 studies published between 2010 and 2022 were included. Pooled incidence was 0.48 cases per 100,000 person-years (95% CI, 0.33-0.63). Subgroup analysis by continent demonstrated a significantly higher incidence of HD in Europe and North America than in Asia. Pooled prevalence was 4.88 per 100,000 (95% CI, 3.38-7.06). Subanalyses by continent demonstrated that the prevalence of HD was significantly higher in Europe and North America than in Africa. The minor increase in prevalence (more so than incidence) demonstrated in this updated review could relate to the enhanced availability of molecular testing, earlier diagnosis, increased life expectancy, and de novo mutations. Limitations include variable case ascertainment methods and lacking case validation data. © 2022 Her Majesty the Queen in Right of Canada. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society. Reproduced with the permission of the Minister of Public Health Agency of Canada.

Population Prevalence, Cancer Risk, and Mortality Risk of Turner Syndrome in South Korean Women Based on National Health Insurance Service Data

PURPOSE

In South Korea, investigations into Turner syndrome (TS) prevalence and TS-associated cancer and mortality are lacking. Accurate data were estimated from the National Health Insurance Service (NHIS) and the Rare Diseases Registry (RDR) records.

MATERIALS AND METHODS

Data on patients with TS who were registered in the RDR between 2007 and 2017 were collected. To estimate TS-associated cancer and mortality risk, the data were compared with data of 1:3 age-matched controls.

RESULTS

In 2017, 2054 patients with TS were identified from a total population of 26186952 South Korean women; therefore, the prevalence was 7.84 per 100000 persons. TS prevalence across 10-year interval age groups were 11.82, 23.17, 18.37, 10.49, 4.09, and 0.38 for age under 10 years, teenagers, 20s, 30s, 40s, and older than 50, respectively (per 100000 persons). The cancer risk in patients with TS was higher than that of age-matched controls over 5.3 person-years [hazard ratio (HR)=1.82, 95% confidence interval (CI) 1.01-3.27, p=0.045]. Among different types of cancer, thyroid cancer risk in patients with TS was significantly higher than that of age-matched controls (HR=2.78, 95% CI 1.06-7.26, p=0.037). We also observed that TS-associated all-cause mortality risk was higher than that of age-matched controls (HR=3.36, 95% CI 1.59-7.10, p=0.002).

CONCLUSION

National prevalence of TS was suggested, and an increased risk of TS-associated thyroid cancer and mortality were observed in this study.

Huntington's Disease in Israel: A Population-Based Study Using 20 Years of Routinely-Collected Healthcare Data

BACKGROUND

Huntington's disease (HD) is a rare, genetic, neurodegenerative disease. Obtaining population-level data on epidemiology and disease management is challenging.

OBJECTIVE

To investigate the epidemiology, clinical manifestations, treatment, and healthcare utilization of patients with HD in Israel.

METHODS

Retrospective population-based cohort study, including 20 years of routinely collected data from Maccabi Healthcare Services, an insurer and healthcare provider for one-quarter of the Israeli population.

RESULTS

The study cohort included 109 adult patients (aged ≥18 years) diagnosed with HD, with mean age of 49.9 years and 56%females. The most common HD-related conditions were anxiety (40%), behavioral problems (34%), sleep disorders (21%), and falls (13%). Annual incidence rates for HD ranged from 0.17 to 1.34 per 100,000 from 2000 to 2018; the 2018 crude prevalence in adults was 4.36 per 100,000. Median survival from diagnosis was approximately 12 years (95%CI: 10.4-15.3). The most frequent symptomatic treatments were antidepressants (69%), antipsychotics (63%), and tetrabenazine (63%), the only drug approved for the treatment of HD chorea in Israel during the examined period. Patterns of healthcare utilization changed as disease duration increased, reflected by increased frequency of emergency department visits and home visits.

CONCLUSION

This retrospective population-based study provides insights into the prevalence, incidence, clinical profile, survival, and resource utilization of patients with HD in ethnically diverse Israel. The findings in this study are generally consistent with the international literature and demonstrate the value of routinely collected healthcare data as a complementary resource in HD research.

Epidemiology of Acute Leukemia among Children with Down Syndrome in Korea

Purpose

Children with Down syndrome (DS) show a higher risk of acute leukemia than those without DS. In this study, we investigated the nationwide incidence of acute leukemia among children with DS and compared their epidemiologic characteristics with those of children with acute leukemia but without DS.

Materials and Methods

Using the National Health Insurance Service database, we selected patients with acute leukemia aged 0–19 years at diagnosis between 2007 and 2016.

Results

Among the 4,697 children with acute leukemia, 54 (1.1%) had DS. The median incidence rate of leukemia with DS by year was 1.3% (range, 0.2% to 2.0%). Sixteen patients with acute lymphoblastic leukemia (ALL; 29.6%) and 36 with acute myeloid leukemia (AML; 66.7%) had DS. The DS group showed younger age at diagnosis than the non-DS group, and diagnosis of AML was more frequent in the DS group than in the non-DS group (3 years vs. 9 years, p < 0.001; 66.7% vs. 32.4%, p < 0.001, respectively). The 5-year overall survival was comparable between the DS and non-DS groups (88.0% vs. 81.9%, p=0.375). Among all the Koreans born between 2007 and 2008, the incidences of acute leukemia, ALL, and AML were 49.25, 20.75, and 163.38 times higher, respectively, in the DS group than in the non-DS group.

Conclusion

Our findings support the fact that the incidence of acute leukemia is higher among patients with DS than among those without DS in Korea. However, the DS and non-DS groups in this study had a comparable overall survival rate.

Contemporary Status of Acute Myocardial Infarction in Korean Patients: Korean Registry of Acute Myocardial Infarction for Regional Cardiocerebrovascular Centers

BACKGROUND

This study aimed to present the development process and characteristics of the Korean Registry of Acute Myocardial Infarction for Regional Cardiocerebrovascular Centers (KRAMI-RCC).

METHODS

We developed KRAMI-RCC, a web-based registry for patients with AMI. Patients from 14 RCCs were registered for more than three years from July 2016. It includes an automatic error-checking system, and user training and on-site monitoring are performed to manage data quality.

RESULTS

A total of 11,700 AMI patients were registered in KRAMI-RCC over three years (73.9% men). The proportions of patients with ST-elevation and non-ST-elevation myocardial infarction at discharge were 43.4% and 56.6%, respectively. Of the total three-year patients, 5.6% died in the hospital, and 4.4% died 12 months after discharge. The case fatality within 12 months was 9.7%. Pre-hospital care data showed delayed arrival time after onset of symptoms (median 153 min) and low transportation rate by public ambulance (25.2%). Post-hospital care data showed lower participation rate in the second rehabilitation program (16.8%).

CONCLUSIONS

The recently developed KRAMI-RCC registry has been more focused on pre-hospital and post-hospital data, which will be helpful in understanding the current state of AMI disease management and in making policy decisions to reduce case fatality in Korea.

Incidence of Huntington disease in a northeastern Spanish region: a 13-year retrospective study at tertiary care centre

Background

Despite the progress in the knowledge of Huntington disease (HD) in recent years, the epidemiology continues uncertain, so the study of incidence becomes relevant. This is important since various factors (type of population, diagnostic criteria, disease-modifying factors, etc.) make these data highly variable. Therefore, the genetic diagnosis of these patients is important, since it unequivocally allows the detection of new cases.

Methods

Descriptive retrospective study with 179 individuals. Incidence of HD was calculated from the ratio of number of symptomatic cases newly diagnosed per 100,000 inhabitants per year during the period 2007–2019 in Aragon (Spain).

Results

50 (27.9%) incident cases of HD (CAG repeat length ≥ 36) were identified from a total of 179 persons studied. The remaining 129/179 (72.1%) were HD negative (CAG repeat length < 36). 29 (58.0%) females and 21 (42.0%) males were confirmed as HD cases. The overall incidence was 0.648 per 100,000 patient-years. 11/50 positive HD cases (22.0%) were identified by performing a predictive test, without clinical symptoms. The minimum number of CAG repeats found was 9 and the most common CAG length among HD negative individuals was 16.

Conclusions

Our incidence lied within the range reported for other Caucasian populations. Implementation of new techniques has allowed to determine the exact number of CAG repeats, which is especially important in patients with triplet expansions in an HD intermediate and/or incomplete penetrance allele, both in diagnostic, predictive and prenatal tests.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12881-020-01174-z.

The Population Prevalence, Associations of Congenital Heart Defect and Mortality Risk for Down's Syndrome in South Korea Based on National Health Insurance Service (NHIS) Data

Background

In the present study, we estimated the population prevalence, associations of congenital heart defect (CHD) and mortality risk for DS using data from National Health Insurance Service (NHIS) and Rare Diseases Registry (RDR).

Methods

We collected data on subjects with DS who were registered in the RDR between 2010 and 2015. To estimate associations of CHD and mortality risk of DS, the data of DS subjects were compared with 1:5 age- and sex-matched controls.

Results

In 2015, 2077 individuals with DS were identified out of the total population of 51,574,044 South Koreans and the prevalence was 4.03 per 100,000 persons. The trend of DS population prevalence across 10-year-old intervals showed a peak in the group under the age of 10 years (26.0 per 100,000 persons) and then declined sharply after the age of 20 years (0.98 per 100,000 persons at 30-39 years of age). In subjects with DS, the frequencies of atrial septal defect [odds ratios (OR) =65.9; 95% CI, 84.1-99.1], ventricular septal defect (OR = 88.1, 95% CI, 57.9-134.1), patent ductus arteriosus (OR = 56.9, 95% CI, 40.1-80.8), tetralogy of fallot (OR = 42.1, 95% CI, 19.3-92.3), or atrioventricular septal defect (OR = 510.0, 95% CI, 126.7-999.0) were higher than those of age- and sex-matched controls. The risk of death in patients with DS was significantly higher than that of age- and sex-matched controls [hazard ratio (HR) =41.7, 95% CI 20.0-87.0].

Conclusion

In South Korea, the DS population prevalence was 4.03 per 100,000 persons in 2015. The subjects with DS were more likely to accompany CHD and have higher mortality risk than healthy controls.

Commonalities in Biological Pathways, Genetics, and Cellular Mechanism between Alzheimer Disease and Other Neurodegenerative Diseases: An In Silico-Updated Overview

BACKGROUND

Alzheimer's disease (AD) is the most common and well-studied neurodegenerative disease (ND). Biological pathways, pathophysiology and genetics of AD show commonalities with other NDs viz. Parkinson's disease (PD), Amyotrophic lateral sclerosis (ALS), Huntington's disease (HD), Prion disease and Dentatorubral-pallidoluysian atrophy (DRPLA). Many of the NDs, sharing the common features and molecular mechanisms suggest that pathology may be directly comparable and be implicated in disease prevention and development of highly effective therapies.

METHOD

In this review, a brief description of pathophysiology, clinical symptoms and available treatment of various NDs have been explored with special emphasis on AD. Commonalities in these fatal NDs provide support for therapeutic advancements and enhance the understanding of disease manifestation.

CONCLUSION

The studies concentrating on the commonalities in biological pathways, cellular mechanisms and genetics may provide the scope to researchers to identify few novel common target(s) for disease prevention and development of effective common drugs for multi-neurodegenerative diseases.

The molecular epidemiology of Huntington disease is related to intermediate allele frequency and haplotype in the general population

Huntington disease (HD) is the most common monogenic neurodegenerative disorder in populations of European ancestry, but occurs at lower prevalence in populations of East Asian or black African descent. New mutations for HD result from CAG repeat expansions of intermediate alleles (IAs), usually of paternal origin. The differing prevalence of HD may be related to the rate of new mutations in a population, but no comparative estimates of IA frequency or the HD new mutation rate are available. In this study, we characterize IA frequency and the CAG repeat distribution in fifteen populations of diverse ethnic origin. We estimate the HD new mutation rate in a series of populations using molecular IA expansion rates. The frequency of IAs was highest in Hispanic Americans and Northern Europeans, and lowest in black Africans and East Asians. The prevalence of HD correlated with the frequency of IAs by population and with the proportion of IAs found on the HD-associated A1 haplotype. The HD new mutation rate was estimated to be highest in populations with the highest frequency of IAs. In European ancestry populations, one in 5,372 individuals from the general population and 7.1% of individuals with an expanded CAG repeat in the HD range are estimated to have a molecular new mutation. Our data suggest that the new mutation rate for HD varies substantially between populations, and that IA frequency and haplotype are closely linked to observed epidemiological differences in the prevalence of HD across major ancestry groups in different countries.

Quantitative Gait Analysis in Patients with Huntington's Disease

Objective

Gait disturbance is the main factor contributing to a negative impact on quality of life in patients with Huntington’s disease (HD). Understanding gait features in patients with HD is essential for planning a successful gait strategy. The aim of this study was to investigate temporospatial gait parameters in patients with HD compared with healthy controls.

Methods

We investigated 7 patients with HD. Diagnosis was confirmed by genetic analysis, and patients were evaluated with the Unified Huntington’s Disease Rating Scale (UHDRS). Gait features were assessed with a gait analyzer. We compared the results of patients with HD to those of 7 age- and sex-matched normal controls.

Results

Step length and stride length were decreased and base of support was increased in the HD group compared to the control group. In addition, coefficients of variability for step and stride length were increased in the HD group. The HD group showed slower walking velocity, an increased stance/swing phase in the gait cycle and a decreased proportion of single support time compared to the control group. Cadence did not differ significantly between groups. Among the UHDRS subscores, total motor score and total behavior score were positively correlated with step length, and total behavior score was positively correlated with walking velocity in patients with HD.

Conclusion

Increased variability in step and stride length, slower walking velocity, increased stance phase, and decreased swing phase and single support time with preserved cadence suggest that HD gait patterns are slow, ataxic and ineffective. This study suggests that quantitative gait analysis is needed to assess gait problems in HD.

Epidemiological Study of Huntington's Disease in the Province of Ferrara, Italy

BACKGROUND

Huntington's disease (HD) is an autosomal dominant neurodegenerative disorder caused by the abnormal expansion of CAG triplet repeat. We aimed to reappraise HD epidemiology in a northern Italian population, in relation to introduction of genetic testing.

METHODS

Through ICD-9M code 333.4 and medical fare exemption code RF0080, HD cases were identified from administrative health data and medical records from the Units of Neurology and Genetics, Ferrara University Hospital, and from other provincial neurological structures.

RESULTS

HD mean annual incidence rate in 1990-2009 was 0.3 per 100,000 (95% CI 0.2-0.5). All incident cases were found to have symptoms of the disease's classic form, and neither juvenile nor the rigid Westphal variant was detected. The mean (SD) age at onset was 50.2 (12.7 years; range 32-82 years), 54.9 (14.6) for men and 45.8 (9.4) for women. On prevalence day, December 31, 2014, HD prevalence was 4.2 per 100,000 (95% CI 2.4-7.0), with a male:female ratio of 1:2.

CONCLUSIONS

The prevalence and incidence of HD in our population were lower than the prevalence and incidence reported for other European and Italian populations, but higher compared to those of Asia, Africa, and Eastern Europe. Compared to previous studies, HD incidence and prevalence did not change significantly.

Survival of Korean Huntington's Disease Patients

OBJECTIVE

The survival of Huntington's disease (HD) patients is reported to be 15-20 years. However, most studies on the survival of HD have been conducted in patients without genetic confirmation with the possible inclusion of non-HD patients, and all studies have been conducted in Western countries. The survival of patients with HD in East Asia, where its prevalence is 10-50-fold lower compared with Western populations, has not yet been reported.

METHODS

Forty-seven genetically confirmed Korean HD patients from independent families were included in this retrospective medical record review study.

RESULTS

The mean age at onset among the 47 patients was 46.1 ± 14.0 years. At the time of data collection, 25 patients had died, and these patients had a mean age at death of 57.8 ± 13.7 years. The Kaplan-Meier estimate of the median survival from onset in the 47 patients was 14.5 years (95% confidence interval: 12.3-16.6). None of the following factors were associated with the survival time in the univariate Cox regression analysis: gender, age at onset, normal CAG repeat size, mutant CAG repeat size, and the absence or presence of non-motor symptoms at onset.

CONCLUSION

This is the first Asian study on survival in HD patients. Survival in Korean HD patients may be shorter than that reported for Western populations, or at least is in the lower range of expected survival. A larger longitudinal observation study is needed to confirm the results found in this study.

The global prevalence of Huntington's disease: a systematic review and discussion

The ascertained prevalence of Huntington's disease (HD) increased significantly following the provision of diagnostic testing. A systematic review was conducted to estimate the prevalence of HD in the post-diagnostic testing era. 22 studies with original data pertaining to the prevalence of HD (1993-2015) were included and analyzed. A global meta-analysis was not performed due to heterogeneity in study methods and geographical variation. The prevalence of HD is significantly lower in Asian populations compared with western Europe, North America and Australia. The global variation in HD prevalence is partly explained by the average CAG repeat lengths and frequency of different HTT gene haplotypes in the general population. Understanding the prevalence of HD has significant implications for healthcare resource planning.

The Epidemiology of Myasthenia Gravis in Korea

PURPOSE

An epidemiological study of myasthenia gravis (MG) has not been performed in Korea. The purpose of this study was to estimate the prevalence and incidence of MG in Korea.

MATERIALS AND METHODS

Health Insurance Review and Assessment (HIRA) data from 2010 to 2014 were searched for MG codes as defined by the International Classification of Diseases, 10th revision. After identifying MG cases, we estimated the prevalence and annual incidence of MG based on the HIRA database and Korean population data.

RESULTS

During the study period, 10138 MG cases were identified. The prevalence of MG was 10.42 cases per 100000 people in 2010 and this increased every year to 12.99 cases per 100000 people in 2014. The average incidence of MG between 2011 and 2014 was 0.69 cases per 100000 person-years. The prevalence and incidence were higher in the older (≥ 50 years) age group than in the younger (<50 years) age group [prevalence: 9.26 vs. 19.24 per 100000, relative risk 2.077, 95% confidence interval (CI) 1.976-2.183, p<0.001; incidence: 0.47 vs. 1.18 per 100000, relative risk 2.490, 95% CI 2.006-3.091, p<0.001].

CONCLUSION

This study was the first nationwide population-based epidemiological study of MG in Korea. The prevalence and incidence of MG were consistent with those of previous studies. We found an increase in the prevalence of MG and a predominance of elderly MG patients.