Introduction
According to the World Health Organization, a rare disease is defined as a condition affecting fewer than 6.5 individuals per 10,000. Often, these diseases have hereditary or congenital origins. Patients with rare diseases frequently exhibit complex symptoms, many of which are neurological in nature [
1]. Despite the identification of numerous rare diseases, the small patient populations for each condition and the diverse range of symptoms pose challenges for early diagnosis. Furthermore, conducting clinical trials with large participant numbers is problematic. Consequently, most rare diseases lack curative treatments, and available therapies tend to be either low in efficacy or expensive. These issues lead to severe disability or death for those affected by rare diseases and contribute to an increased socioeconomic burden [
2].
In this study, we sought to establish a registry for motor neuron disease, hereditary spastic paraplegia (HSP), and spinocerebellar ataxia (SCA). These rare motor nervous system disorders are characterized by gait disturbance as a primary symptom. Although these diseases are respectively typified by muscle weakness, spastic paraplegia, and ataxia, they can present with a spectrum of overlapping motor neuron symptoms with similar initial clinical presentations. Furthermore, the absence of precise diagnostic biomarkers and identified genetic variants complicates the accuracy of diagnosis.
Amyotrophic lateral sclerosis (ALS) is a rare and incurable neurodegenerative disease that affects motor nerves in the cerebrum, brainstem, and spinal cord. The clinical manifestations of ALS are highly heterogeneous. Depending on the primary site of pathogenesis, patients may be classified as having progressive muscular atrophy, primary lateral sclerosis, or bulbar ALS [
3]. However, because the diagnosis of ALS is based on clinical diagnostic criteria, it is difficult to distinguish the early stages of this disease from other conditions with similar clinical manifestations, such as progressive paraplegia and spinocerebellar atrophy [
4]. Moreover, a definitive diagnosis of ALS is often elusive until symptoms have fully progressed [
5–
7]. According to Brown et al. [
8], the pooled prevalence rate of ALS (per 100,000 people) is 6.22 in Europe, 5.20 in North America, and 3.01 in Asia, excluding Japan. Approximately 5.1% of ALS cases are considered familial ALS, with the remainder classified as sporadic ALS [
8,
9]. Research on familial ALS has identified major pathogenic mutations in genes associated with the disease, such as
SOD1 and
C9ORF72. While these pathogenic mutations are rare, they have also been found in patients with sporadic ALS. Furthermore, recent findings confirm that ALS clinically and genetically overlaps with several multisystem neurodegenerative diseases [
3]. Consequently, research into hereditary ALS is intensifying in an effort to enhance our understanding of the disease and to discover suitable treatments. In the Republic of Korea, the prevalence of ALS is approximately 3 per 100,000 people, markedly lower than in Western countries [
10]. The genotypes identified in the Republic of Korea are predominantly
SOD1 genetic variants, in contrast to the
C9ORF72 variants that are more common in Western populations, underscoring a key regional difference in the genetic landscape of the disease [
11]. Therefore, collecting clinical and genetic information on Korean patients with ALS is necessary to develop treatments appropriate for this population. To achieve this, a network of ALS researchers must be established and sustained with ongoing support, focusing on the development of diagnostics and therapies.
HSP encompasses a group of inherited neurological disorders that affect the corticospinal tract, leading to stiffness and muscle weakness in the lower limbs. Epidemiological data on HSP are scarce due to its ambiguous clinical diagnosis and classification. However, the prevalence of HSP with a confirmed genetic mutation is approximately 1.8 per 100,000 individuals [
12]. HSP prevalence exhibits considerable regional variation, with figures as low as 0.2 per 100,000 in Japan, potentially indicating a lower incidence in Eastern than in Western populations [
13]. HSP can be classified based on clinical phenotype, inheritance pattern, or pathogenesis [
14]. From a clinical perspective, HSPs are divided into pure and complex forms. Pure HSP typically presents with progressive spastic weakness of the lower limbs, hypertonic urinary bladder disturbance, and a mild reduction in vibratory sensation. In contrast, complex HSP may include additional clinical features such as cerebellar dysfunction, cognitive impairment, peripheral neuropathy, and dyskinesia, alongside the characteristic lower limb spastic paralysis. It is therefore important to differentiate HSP from conditions such as motor neuron disease, dementia, and genetic metabolic disorders. Regarding inheritance patterns, HSPs are classified as autosomal dominant, autosomal recessive, sex chromosome-linked, or mitochondrial. The genetic landscape of HSP is diverse, and associations between phenotype and genotype are often unclear. In many instances, genetic variants remain unidentified even when the clinical presentation is consistent with HSP. Consequently, gathering clinical and biological data from patients in the Republic of Korea is vital for advancing our understanding of this condition.
SCA encompasses a clinically and genetically diverse group of autosomal dominant inherited degenerative disorders affecting the cerebellum and its associated structures. SCA represents one of the rarest incurable diseases. The disease primarily affects the cerebellum and progresses to cause a range of cerebellar-related dysfunctions, such as gait disturbances, hand tremors, dysarthria, dysphagia, and balance issues [
15]. Due to its rarity, data on national prevalence rates are scarce and variable [
16]. In the Republic of Korea, a study estimated the prevalence of SCA to be 4.99 per 100,000 person-years, based on data from the Korean National Health Insurance system [
17]. Another study investigating the distribution of SCA genes in this country identified
SCA2,
SCA3, and
SCA6 as the most prevalent [
18]. However, despite the publication of several Korean studies, including multicenter research utilizing National Health Insurance data, few registries or databases detail the clinical presentation of patients with SCA. Consequently, a critical need exists to establish a registry for Korean patients with SCA. Research into actual clinical presentations can yield valuable evidence for future treatment and care, while supporting the development of initiatives to improve the welfare and legal systems necessary to improve the lives of patients.
Each of the diseases mentioned is rare and characterized by motor symptoms, with numerous genetic variants identified. Consequently, diagnosing based on a single genetic test is challenging, as different genes can lead to a range of clinical manifestations, and phenotypes may overlap across multiple genes (
Figure 1). Moreover, genotype distributions vary between national and international reports. With the continuous discovery of new genetic variants, it is essential to gather and share diverse patient information for long-term research. This will enable a more comprehensive understanding along with integration into clinical practice [
19].
Overall, epidemiological data on rare motor neuron diseases are limited due to their low prevalence, the complexities of clinical diagnosis, their unclear pathogenesis, and their genetic heterogeneity. Identifying biomarkers and developing targeted therapeutics are further complicated by these factors. Therefore, the need exists to create a comprehensive registry and to gather robust evidence on risk factors and early diagnosis through research efforts. To address this need, the present study was designed to establish a registry for rare neurological diseases in the Republic of Korea and to construct a biobank of high-quality human bioresources. This registry is termed the Korean Research Network for Motor Neuron Disease and Spinocerebellar Ataxia (K-MoSCA). The study also entails the development of an expert network that will lay the groundwork for a range of future studies in this field.
Collection
Five tertiary hospitals in the Republic of Korea will participate in the data collection process: Konkuk University Medical Center, Samsung Medical Center, Chungnam National University Hospital, Soonchunhyang University Cheonan Hospital, and Inje University Haeundae Paik Hospital (
Figure 2). Each research center has individually obtained approval from its respective institutional review board. Our goal is to gather data from patients who have been diagnosed with the specified rare diseases within the Department of Neurology at each hospital and who have voluntarily consented to participate in the study. We are aiming for a total of 60 study participants annually over a period of 3 years, amounting to 180 participants in total, with each hospital contributing 12 participants per year. Data collection will take place at each institution over a 3-year period commencing on the date of approval by the ethics committee of each institution. Additionally, information will be collected from patients who are willing to participate in the study during their baseline visit and at 6-month follow-up appointments.
Patients who agree to participate in the study will provide written informed consent and will receive a copy of the consent form. Potential participants will be clearly informed that their decision to participate or decline will not affect their clinical care. They will also be told that they have the right to withdraw their consent at any time before data collection is finalized. Patients will be given the contact details of the research team, allowing them to withdraw without the need to discuss their decision with others. Research staff will be made aware that patients may refuse to participate and withdraw their consent at any point before the completion of data collection.
Participants must be at least 19 years old and have a diagnosis of ALS, HSP, or SCA. For those with ALS, eligibility will be determined based on whether they meet any of the following diagnostic requirements: the Revised El Escorial criteria, the Awaji Criteria, or the Gold Coast Criteria [
5–
7]. Patients with HSP or SCA will be considered eligible if they possess relevant genetic variants and exhibit a clinical presentation that aligns with their diagnosis [
12,
15]. Enrollment of participants with these conditions will occur after they have completed adequate differential diagnostic testing, as determined by the investigating researcher. Conversely, individuals with other systemic diseases, vulnerable populations such as minors or those with cognitive impairments, participants from whom clinical information and biological samples cannot be obtained, and any individuals deemed unsuitable for the study by the investigator will be excluded (
Table 1).
After consenting to participate in the study, during the initial visit, patients will be asked to provide a range of information. These data include demographics, personal medical history, family history, comorbidities, clinical information, treatment details, disability assessments, and patient-based quality of life measures obtained through questionnaires (
Table 2). Disability assessments will employ disease-specific scales: the Korean version of the Revised Amyotrophic Lateral Sclerosis Functional Rating Scale (K-ALSFRS-R) for ALS, the Spastic Paraplegia Rating Scale (SPRS) for HSP, and the Scale for the Assessment and Rating of Ataxia (SARA) for SCA [
20–
22]. Quality of life will be evaluated using the Fatigue Severity Scale, the Beck Depression Inventory-II, the Pittsburgh Sleep Quality Index, the World Health Organization Quality of Life-BREF, and the Korean version of the Zarit Burden Interview as a measure of caregiver burden [
23–
26].
Patient clinical information will be de-identified, and all centers will utilize a standardized case record form. These case notes will document standard demographic data, categorized by disease, and a registry will be established via a web-based clinical research management system (iCreaT;
https://icreat.nih.go.kr/) [
27]. To ensure the efficient operation of this system, each institutional researcher will receive training on its use and be assigned identification.
Prospectively, blood samples and (when possible) cerebrospinal fluid will be collected. Each blood sample will consist of approximately 25 mL, distributed as follows: 3 ethylenediaminetetraacetic acid (EDTA) tubes (12 mL total), 1 serum separator tube (8 mL), and 1 Paxgene tube (5 mL). An additional 10 mL of blood will be collected and stored if patients consent to provide peripheral blood mononuclear cells and RNA. The blood in the EDTA tubes will be separated into DNA (10 μg per vial in 3 vials), plasma (300 μL per vial in 10 vials), and buffy coat (1.8 mL in a single vial). The blood in the serum separator tube will be processed to obtain serum (300 μL per vial in 5 vials). From the Paxgene RNA tube, 3 to 4 mL of RNA-stabilized blood will be extracted. Furthermore, if a lumbar puncture is performed for medical treatment or diagnosis and the patient consents, approximately 5 to 10 mL of cerebrospinal fluid will be collected. No cerebrospinal fluid will be collected solely for research purposes, and this material will only be stored if an excess is available over the amount required for medical procedures. Blood and cerebrospinal fluid samples will be collected, processed, and stored by the Global Clinical Central Lab and then sent to the National Biobank of Korea annually [
28]. At each 6-month follow-up, clinical scales will be reassessed for each disease. Additional information will be gathered regarding wheelchair use, gastrostomy, tracheostomy, and, if applicable, the date of death.
Strengths and Weaknesses
The aim of this study was to develop the first registry focused on rare neurological diseases affecting the motor nervous system in the Republic of Korea. We have created a web-based platform that facilitates multi-institutional collaboration within this country, allowing for the collection of patient information on rare conditions. Previously, these data were managed independently by each institution for individual diseases. By focusing exclusively on rare motor nerve diseases and engaging experts from various institutions, we anticipate that specialized data can be more easily gathered and shared. Moreover, a broad range of data will be obtained through initial evaluation questionnaires that cover depression, sleep, quality of life, and caregiver burden. This approach is expected to aid in the identification of potential biomarkers and the discovery of genetic variants that are prevalent in the Korean population. Additional data acquired from patient follow-ups will further enhance our understanding of the epidemiology of rare movement disorders in the Republic of Korea. The insights gained from this data will help to facilitate early diagnosis, determine the appropriate timing of medical intervention, establish patient-centered management strategies, and inspire the development of novel treatments. In Europe, national registries for rare diseases, including neurological conditions, have been established. These registries facilitate information sharing, the development of diagnostic and management guidelines, and the provision of training programs based on these guidelines [
29]. It is our hope that these European models will inform the creation of national registries in Asia and provide a valuable resource to support personalized medicine for patient populations that differ from those in Western countries.
Our registry has the potential to be utilized for expanded studies of the targeted diseases. Data will be collected from patients and their progress monitored under current standards of care, aiding in the identification of progressive genetic variants and analyses of treatment effectiveness in Korean patients. Additionally, it will provide information on cost-effective testing and the tracking of highly relevant biomarkers and genes for patients who are unable to participate. Biomarker monitoring, the application of new therapeutic agents, and appropriate gene therapy are expected to be prioritized to help surviving patients, and the existing genetic information can assist in the analysis of subgroups for each disease.
Ultimately, the registry will serve as a basis for medical policy decisions concerning motor neuron diseases and related disorders. It is designed to gather data on the diagnostic process and medical treatments for each rare disease. Additionally, extending our research to include the estimation of healthcare costs associated with diagnosis, treatment, and medical intervention could form a foundation for future health insurance budget allocations and coverage policies. Additionally, the registry will compile data on factors such as fatigue, sleep patterns, depression, quality of life, and caregiver burden. This information will be instrumental in understanding the real-world needs of patients and their caregivers, allowing for the prioritization of services and the reform of relevant policies.
The study does have certain limitations. Like other registries, it offers no direct benefits to participating patients. Those enrolled in the registry and contributing specimens will not gain direct financial or therapeutic incentives. They should not anticipate any specific benefits until new treatments are formulated from the analysis of their provided data, or until they are assessed for suitable interventions. These points are clearly communicated in the informed consent documentation.
Participant selection bias within the registry is also a possibility. The number of participating centers is limited, and not all patients diagnosed at each center can be enrolled. Moreover, as outlined in the exclusion criteria, patients experiencing cognitive decline who do not have a guardian are not suitable for inclusion in the registry, as it is unlikely that sufficient information can be obtained from them. Additionally, the limited participant capacity and brief enrollment window mean that patients diagnosed outside of this period, as well as those diagnosed after the target number of patients has been reached, will be excluded from the registry, potentially contributing to bias. Geographically, 2 of the 5 centers are situated in Seoul; this complicates the process of evenly recruiting patients from each region, especially when factoring in travel distance. Patients who are more educated, younger, have better mobility, or have caregivers who can readily travel to the centers and are attuned to their medical needs are relatively likely to be represented in the registry.
Limitations in the maintenance and persistence of the registry should also be expected. Enrolled patients will undergo follow-up every 6 months to evaluate their clinical symptoms, clinical measures, and the utilization of invasive treatments. However, we anticipate challenges in data management and updates following the conclusion of the 3-year study period. The diagnosis and classification of individual rare diseases may evolve, and the registry may only partially capture these changes for patients whose initial diagnosis is subject to revision due to new findings over the course of the study. Additionally, compatibility with registries from other healthcare organizations and forthcoming advancements should be considered.
, Sooyoung Kim2
