Nationwide incidence of myotonic dystrophy type 1 and the status of multi-organ involvement

Myotonic dystrophy type 1 in South Korea: a comprehensive analysis of cancer and comorbidity risks

BACKGROUND AND PURPOSE

Myotonic dystrophy type 1 (DM1) is an inherited neuromuscular disorder characterized by myotonia and progressive muscle weakness. Beyond the primary symptoms, there is growing concern regarding a higher incidence of certain comorbidities in DM1 patients, including cancer, diabetes, thyroid dysfunction, and cataracts. This study was designed to examine the occurrence of these conditions among patients diagnosed with DM1 in South Korea, using data from the National Health Insurance Service database.

METHODS

The study undertook a comprehensive review of 3,842 patients diagnosed with DM1 between 2012 and 2018. We assessed the incidence of cancer and the prevalence of diabetes, thyroid dysfunction, and cataracts among these patients, comparing their rates to those in the general population.

RESULTS

In the study cohort, 463 out of 3,842 DM1 patients (12.04%) were diagnosed with cancer, indicating a substantial elevation in cancer risk with an overall standard incidence ratio of 1.9 (95% CI = 1.6-2.3, p < 0.01) when compared to the expected rates in the general population. Moreover, the prevalence of diabetes (15.2%) and thyroid dysfunction (17.6%) was noteworthy in the DM1 population. The mean age at which DM1 patients underwent cataract surgery was 55.07 years, noticeably younger than the mean age of 69.25 years for cataract surgery in the general population.

CONCLUSIONS

DM1 patients have a noteworthy occurrence of several comorbidities such as cancer, diabetes, thyroid dysfunction, and earlier cataract surgery. This highlights the importance of a comprehensive and integrative approach to the management and treatment of DM1, going beyond addressing only the primary neuromuscular symptoms. More research is required to understand the underlying mechanisms contributing to these comorbidities in DM1 patients, which may inform preventative measures and guide improvements in patient care.

Clinical features and genetic spectrum of a multicenter Chinese cohort with myotonic dystrophy type 1

BACKGROUND

As the most common subtype of adult muscular dystrophy worldwide, large cohort reports on myotonic dystrophy type I (DM1) in China are still lacking. This study aims to analyze the genetic and clinical characteristics of Chinese Han DM1 patients.

METHODS

Based on the multicenter collaborating effort of the Pan-Yangtze River Delta Alliance for Neuromuscular Disorders, patients with suspected clinical diagnoses of DM1 were genetically confirmed from January 2020 to April 2023. Peak CTG repeats in the DMPK gene were analyzed using triplet repeat-primed PCR (TP-PCR) and flanking PCR. Time-to-event analysis of onset age in females and males was performed. Additionally, detailed clinical features and longitudinal changes from the disease onset in 64 DM1 patients were retrospectively collected and analyzed. The Epworth Sleepiness Scale and Fatigue Severity Scale were used to quantify the severity of daytime sleepiness and fatigue.

RESULTS

Among the 211 genetically confirmed DM1 patients, the mean age at diagnosis was 40.9 ± 12.2 (range: 12-74) with a male-to-female ratio of 124:87. The average size of CTG repeats was 511.3 (range: 92-1945). Among the DM1 patients with comprehensive clinical data (n = 64, mean age 41.0 ± 12.0), the age at onset was significantly earlier in males than in females (4.8 years earlier, p = 0.026). Muscle weakness (92.2%), myotonia (85.9%), and fatigue (73.4%) were the most prevalent clinical features. The predominant involved muscles at onset are hands (weakness or myotonia) (52.6%) and legs (walking disability) (42.1%). Of them, 70.3% of patients had daytime sleepiness, 14.1% had cataract surgery, 7.8% used wheelchairs, 4.7% required ventilatory support, and 1.6% required gastric tubes. Regarding the comorbidities, 4.7% of patients had tumors, 17.2% had diabetes, 23.4% had dyspnea, 28.1% had intermittent insomnia, 43.8% experienced dysphagia, and 25% exhibited cognitive impairment. Chinese patients exhibited smaller size of CTG repeats (468 ± 139) than those reported in Italy (613 ± 623), the US (629 ± 386), and Japan (625 [302, 1047]), and milder phenotypes with less multisystem involvement.

CONCLUSION

The Chinese Han DM1 patients presented milder phenotypes compared to their Caucasian and Japanese counterparts. A male predominance and an early age of onset were identified in male Chinese Han DM1 patients.

Nationwide-incidence and trends of fibromyalgia in South Korea: a population-based study

Reports of the incidence of fibromyalgia (FM) in Asia are uncommon. Therefore, this study used nationwide representative data to investigate the age- and sex-specific incidence and annual trends of FM in South Korea. This nationwide population-based study used data from the Korean National Health Claims Database. From 2012 to 2021, patients with FM diagnosed according to the ACR 2010 criteria from the entire Korean population aged 20-70 years were included in the enrolment database. Age- and sex-specific cumulative and annual incidences were analyzed and incident cases from 2014 to 2021 were included, considering the 2-year washout period. Among the total cohort of 42 million in the entire Korean population, 270,160 had FM during the study period. The incidence in the general population aged 20-70 years was 751.25 (95% confidence interval [CI] 751.10-751.40) per 100,000 persons (men: 95% CI 608.45-608.98; women: 95% CI 898.02-898.69). The incidence of FM increased with advancing age, peaking at 50-54 years both in men and women. The annual incidence was 88.07 (95% CI 88.02-88.13) in 2014; it increased from 2014 to 2019 and peaked in 2019 (109.20; 95% CI 101.65-101.76). The incidence of FM in South Korea was about twice the global average, with a gradual increase over the study period. These detailed estimates can help with proper planning within the healthcare system.

Intergenerational Influence of Gender and the DM1 Phenotype of the Transmitting Parent in Korean Myotonic Dystrophy Type 1

Myotonic dystrophy type 1 (DM1) is the most common autosomal-dominant disorder caused by the CTG repeat expansion of the DMPK, and it has been categorized into three phenotypes: mild, classic, and congenital DM1. Here, we reviewed the intergenerational influence of gender and phenotype of the transmitting parent on the occurrence of Korean DM1. A total of 44 parent–child pairs matched for the gender of the transmitting parent and the affected child and 29 parent–child pairs matched for the gender and DM1 phenotype of the transmitting parent were reviewed. The CTG repeat size of the DMPK in the affected child was found to be significantly greater when transmitted by a female parent to a female child (DM1-FF) (median, 1309 repeats; range, 400–2083) than when transmitted by a male parent to a male child (650; 160–1030; p = 0.038 and 0.048 using the Tukey HSD and the Bonferroni test) or by a male parent to a female child (480; 94–1140; p = 0.003). The difference in the CTG repeat size of the DMPK between the transmitting parent and the affected child was also lower when transmitted from a male parent with classic DM1 (−235; −280 to 0) compared to when it was transmitted from a female parent with mild DM1 (866; 612–905; p = 0.015 and 0.019) or from a female parent with classic DM1 (DM1-FC) (605; 10–1393; p = 0.005). This study highlights that gender and the DM1 phenotype of the transmitting parent had an impact on the CTG repeat size of the DMPK in the affected child, with greater increases being inherited from the DM1-FF or DM1-FC situations in Korean DM1.