Prevalence of myotonic dystrophy in Israeli Jewish communities: inter-community variation and founder premutations

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.

A Nationwide, Population-Based Prevalence Study of Genetic Muscle Disorders

BACKGROUND

Previous epidemiological studies of genetic muscle disorders have relied on medical records to identify cases and may be at risk of selection biases or have focused on selective population groups.

OBJECTIVES

This study aimed to determine age-standardised prevalence of genetic muscle disorders through a nationwide, epidemiological study across the lifespan using the capture-recapture method.

METHODS

Adults and children with a confirmed clinical or molecular diagnosis of a genetic muscle disorder, resident in New Zealand on April 1, 2015 were identified using multiple overlapping sources. Genetic muscle disorders included the muscular dystrophies, congenital myopathies, ion channel myopathies, GNE myopathy, and Pompe disease. Prevalence per 100,000 persons by age, sex, disorder, ethnicity and geographical region with 95% CIs was calculated using Poisson distribution. Direct standardisation was applied to age-standardise prevalence to the world population. Completeness of case ascertainment was determined using capture-recapture modelling.

RESULTS

Age standardised minimal point prevalence of all genetic muscle disorders was 22.3 per 100,000 (95% CI 19.5-25.6). Prevalence in Europeans of 24.4 per 100,000, (95% CI 21.1-28.3) was twice that observed in NZ's other 3 main ethnic groups; Māori (12.6 per 100,000, 95% CI 7.8-20.5), Pasifika (11.0 per 100,000, 95% CI 5.4-23.3), and Asian (9.13 per 100,000, 95% CI 5.0-17.8). Crude prevalence of myotonic dystrophy was 3 times higher in Europeans (10.5 per 100,000, 9.4-11.8) than Māori and Pasifika (2.5 per 100,000, 95% CI 1.5-4.2 and 0.7 per 100,000, 95% CI 0.1-2.7 respectively). There were considerable regional variations in prevalence, although there was no significant association with social deprivation. The final capture-recapture model, with the least deviance, estimated the study ascertained 99.2% of diagnosed cases.

CONCLUSIONS

Ethnic and regional differences in the prevalence of genetic muscle disorders need to be considered in service delivery planning, evaluation, and decision making.

Core Clinical Phenotypes in Myotonic Dystrophies

Myotonic dystrophy type 1 (DM1) and type 2 (DM2) represent the most frequent multisystemic muscular dystrophies in adulthood. They are progressive, autosomal dominant diseases caused by an abnormal expansion of an unstable nucleotide repeat located in the non-coding region of their respective genes DMPK for DM1 and CNBP in DM2. Clinically, these multisystemic disorders are characterized by a high variability of muscular and extramuscular symptoms, often causing a delay in diagnosis. For both subtypes, many symptoms overlap, but some differences allow their clinical distinction. This article highlights the clinical core features of myotonic dystrophies, thus facilitating their early recognition and diagnosis. Particular attention will be given to signs and symptoms of muscular involvement, to issues related to respiratory impairment, and to the multiorgan involvement. This article is part of a Special Issue entitled “Beyond Borders: Myotonic Dystrophies—A European Perception.”

The Epidemiology of Neuromuscular Diseases

Neuromuscular disorders as a group are linked by anatomy with significant differences in pathogenetic mechanisms, clinical expression, and time course of disease. Each neuromuscular disease is relatively uncommon, yet causes a significant burden of disease socioeconomically. Epidemiologic studies in different global regions have demonstrated certain neuromuscular diseases have increased incidence and prevalence rates over time. Understanding differences in global epidemiologic trends will aid clinical research and policies focused on prevention of disease. There is a critical need to understand the global impact of neuromuscular diseases using metrics currently established for communicable and noncommunicable diseases.

A Systematic Review and Meta-analysis on the Epidemiology of the Muscular Dystrophies

Background: The muscular dystrophies are a heterogeneous group of genetic muscle diseases with variable distribution of weakness and mode of inheritance.Methods: We previously performed a systematic review of worldwide population-based studies on Duchenne and Becker muscular dystrophies; the current study focused on the epidemiology of other muscular dystrophies using Medline and EMBASE databases. Two reviewers independently reviewed all abstracts, full-text articles, and abstracted data from 1985 to 2011. Pooling of prevalence estimates was performed using random-effect models.Results: A total of 1104 abstracts and 167 full-text articles were reviewed. Thirty-one studies met all eligibility criteria and were included in the final analysis. The overall pooled prevalence of combined muscular dystrophies was 16.14 (confidence interval [CI], 11.21-23.23) per 100,000. The prevalence estimates per 100,000 were 8.26 (CI, 4.99-13.68) for myotonic dystrophy, 3.95 (CI, 2.89-5.40) for facioscapulohumeral dystrophy, 1.63 (CI, 0.94-2.81) for limb girdle muscular dystrophy, and 0.99 (CI, 0.62-1.57) for congenital muscular dystrophies.Conclusions: The studies differed widely in their approaches to case ascertainment, and substantial gaps remain in the global estimates of many other types of muscular dystrophies. Additional epidemiological studies using standardized diagnostic criteria as well as multiple sources of case ascertainment will help address the economic impact and health care burden of muscular dystrophies worldwide.

Increased cancer risks in myotonic dystrophy

OBJECTIVE

To estimate cancer risks for patients with myotonic dystrophy, given that increased risks for neoplasms in association with myotonic dystrophy type 1 and type 2 have been suggested in several studies but the risks of cancers have not been quantified.

PATIENTS AND METHODS

A cohort of 307 patients with myotonic dystrophy identified from medical records of Mayo Clinic in Rochester, MN, from January 1, l993, through May 28, 2010, was retrospectively analyzed. We estimated standardized incidence ratios (SIRs) of specific cancers for patients with myotonic dystrophy compared with age- and sex-specific cancer incidences of the general population. Age-dependent cumulative risks were calculated using the Kaplan-Meier method.

RESULTS

A total of 53 cancers were observed at a median age at diagnosis of 55 years. Patients with myotonic dystrophy had an increased risk of thyroid cancer (SIR, 5.54; 95% confidence interval [CI], 1.80-12.93; P=.001) and choroidal melanoma (SIR, 27.54; 95% CI, 3.34-99.49; P<.001). They may also have an increased risk of testicular cancer (SIR, 5.09; 95% CI, 0.62-18.38; P=.06) and prostate cancer (SIR, 2.21; 95% CI, 0.95-4.35; P=.05). The estimated cumulative risks at age 50 years were 1.72% (95% CI, 0.64%-4.55%) for thyroid cancer and 1.00% (95% CI, 0.25%-3.92%) for choroidal melanoma. There was no statistical evidence of an increased risk of brain, breast, colorectal, lung, renal, bladder, endometrial, or ovarian cancer; lymphoma; leukemia; or multiple myeloma.

CONCLUSION

Patients with myotonic dystrophy may have an increased risk of thyroid cancer and choroidal melanoma and, possibly, testicular and prostate cancers.

Population frequency of myotonic dystrophy: higher than expected frequency of myotonic dystrophy type 2 (DM2) mutation in Finland

Myotonic dystrophy (DM) is the most common adult-onset muscular dystrophy with an estimated prevalence of 1/8000. There are two genetically distinct types, DM1 and DM2. DM2 is generally milder with more phenotypic variability than the classic DM1. Our previous data on co-segregation of heterozygous recessive CLCN1 mutations in DM2 patients indicated a higher than expected DM2 prevalence. The aim of this study was to determine the DM2 and DM1 frequency in the general population, and to explore whether the DM2 mutation functions as a modifier in other neuromuscular diseases (NMD) to account for unexplained phenotypic variability. We genotyped 5535 Finnish individuals: 4532 normal blood donors, 606 patients with various non-myotonic NMD, 221 tibial muscular dystrophy patients and their 176 healthy relatives for the DM2 and DM1 mutations. We also genotyped an Italian idiopathic non-myotonic proximal myopathy cohort (n = 93) for the DM2 mutation. In 5496 samples analyzed for DM2, we found three DM2 mutations and two premutations. In 5511 samples analyzed for DM1, we found two DM1 mutations and two premutations. In the Italian cohort, we identified one patient with a DM2 mutation. We conclude that the DM2 mutation frequency is significantly higher in the general population (1/1830; P-value = 0.0326) than previously estimated. The identification of DM2 mutations in NMD patients with clinical phenotypes not previously associated with DM2 is of particular interest and is in accord with the high overall prevalence. On the basis of our results, DM2 appears more frequent than DM1, with most DM2 patients currently undiagnosed with symptoms frequently occurring in the elderly population.

Epidemiology of myotonic dystrophy type 1 (Steinert disease) in Belgrade (Serbia)

The aim of this study was to estimate the incidence and prevalence of myotonic dystrophy type 1 (DM1) in Belgrade during the period 1983-2002. The patients who had DM1 were ascertained through hospital records from all neurological departments in Belgrade during 1983-2002. The molecular genetic analysis was performed in all patents included in the study. We identified 101 DM1 patients (52 males and 49 females). The average annual incidence rate of DM1 in Belgrade for the period observed was 2.0/1,000,000 (95% confidence interval (CI), 0.3-8.3), 2.1/1,000,000 (95% CI, 0.3-8.3) for males and 2.0/1,000,000 (95% CI, 0.3-8.3) for females. The highest age-specific DM1 incidence was registered in the age group 20-49: 3.4/1,000,000 (95% CI, 0.5-7.6), 4.0/1,000,000 (95% CI, 1.1-10.2) in males and 2.5/1,000,000 (95% CI, 0.5-7.6) in females. In the population of Belgrade, a cumulative probability of acquiring DM1 was 1 per 8621 for men and 1 per 9259 for women (1 per 8940 of the population for both sexes). The prevalence of DM1 in Belgrade on 31 December 2002 was 5.3/100,000 (95% CI, 4.2-6.6).

A neonatal form of Steinert's myotonic dystrophy in twins after in vitro fertilization

OBJECTIVE

To report a case of nonidentical twins affected with a congenital form of Steinert's myotonic dystrophy (DM1), conceived by IVF owing to parental sterility, in which the mother presented a paucisymptomatic form of DM1 which was diagnosed as a result of the condition inherited by the twins.

DESIGN

Case report.

SETTING

Neonatal intensive care unit of a tertiary hospital.

PATIENT(S)

Newborn twins affected with the congenital form of DM1 and a 35-year-old nulliparous mother.

INTERVENTION(S)

In vitro fertilization.

MAIN OUTCOME MEASURE(S)

Molecular study of the CTG triplet expansion related with DM1.

RESULT(S)

Molecular study evidenced a pathologic expansion in both twins as well as in their mother.

CONCLUSION(S)

This case should serve as a reminder to practitioners that assisted reproductive techniques have opened the possibility that asymptomatic or paucisymptomatic carriers of a genetic syndrome can inadvertently conceive fetuses affected with more serious forms of the illness.

Anatomy of a founder effect: myotonic dystrophy in Northeastern Quebec

Founder effects are largely responsible for changes in frequency profiles of genetic variants in local populations or isolates. They are often recognized by elevated incidence of certain hereditary disorders as observed in regions of Charlevoix and Saguenay-Lac-Saint-Jean (SLSJ) in Northeastern Quebec. Dominantly transmitted myotonic dystrophy (DM1) is highly prevalent in SLSJ where its carrier rate reaches 1/550, compared with 1/5,000 to 1/50,000 elsewhere. To shed light on the origin of DM1 in this region, we have screened 50 nuclear DM1 families from SLSJ and studied the genetic variation in a 2.05 Mb (2.9 cM) segment spanning the site of the expansion mutation. The markers analyzed included 22 biallelic SNPs and two microsatellites. Among 50 independent DM1 chromosomes, we distinguished ten DM1-associated haplotypes and grouped them into three haplotype families, A, B and C, based on the relevant extent of allele sharing between them. To test whether the data were consistent with a single entry of the mutation into SLSJ, we evaluated the age of the founder effect from the proportion of recombinant haplotypes. Taking the prevalent haplotype A1_21 (58%) as ancestral to all the disease-associated haplotypes in this study, the estimated age of the founder effect was 19 generations, long predating the colonization of Nouvelle-France. In contrast, considering A1_21 as ancestral to the haplotype family A only, yielded the estimated founder age of nine generations, consistent with the settlement of Charlevoix at the turn of 17th century and subsequent colonization of SLSJ. We conclude that it was the carrier of haplotype A (present day carrier rate of 1/730) that was a "driver" of the founder effect, while minor haplotypes B and C, with corresponding carrier rates of 1/3,000 and 1/10,000, respectively, contribute DM1 to the incidence level known in other populations. Other studies confirm that this might be a general scenario in which a major "driver" mutation/haplotype issued from a founder effect is found accompanied by distinct minor mutations/haplotypes occurring at background population frequencies.

Cancer in Jews: introduction and overview

This article is based upon a literature overview of cancer in Jews. It involves a comparison of variation in incidence and prevalence rates between Jews and non-Jews. However, the reader must exercise a certain amount of skepticism when considering secular changes in cancer incidence and prevalence and the public health implications of such cancer variation. Ashkenazi Jews have a lifetime CRC risk of 9--15%. This elevated CRC risk is similar to that of individuals in the "familial risk'' category, and differs strikingly from the 5-6% CRC risk for non-Ashkenazi members of general Western populations. A MedLine search tested the hypothesis that site-specific and/or all-cancer incidence and mortality rates are either higher or lower than expected in Ashkenazi Jews worldwide, when compared with reference populations. Results showed that all cancer incidence and mortality is not higher in Ashkenazi Jews when compared to North American non-Hispanic whites. Indeed, rates for some cancers, such as carcinoma of the lung in Ashkenazi males, are low; this example is likely attributable in large part to decreased tobacco use. Carcinoma of the ovary, pancreas, stomach, and non-Hodgkin's lymphoma have a higher incidence rate in Ashkenazi. Even though BRCA1 and BRCA2 founder mutations which predispose to carcinoma of the breast and ovary appear increased in Ashkenazi breast cancer affected women, there was no evidence supporting an elevated risk of breast cancer among Ashkenazi women. Our primary concern, however, is that Ashkenazi Jews may have one of the highest lifetime CRC risks of any ethnic group in the world, a risk that diverges significantly from that of the general population; therein, it logically calls for more intensive CRC screening guidelines. We have emphasized that the reader use caution in the interpretation of statistics which portray variation in incidence and prevalence figures for cancer in any racial, ethnic, or religious group, inclusive, of course, of Jews. Clearly, more research will be required in the interest of accuracy in the understanding of these cancer variations, since they portend the need for special cancer control strategies. A lesser degree of attention can then be given to carcinoma of the penis and uterine cervix, which occur very infrequently in Jews. We urge our colleagues to continue to probe further into these statistical differences in cancer's incidence and prevalence in order to garner a better understanding of cancer's etiology and pathogenesis.