Prenatal diagnosis in myotonic dystrophy type 1. Thirteen years of experience: implications for reproductive counselling in DM1 families

Gender disparities in myotonic dystrophy 1

Myotonic Dystrophy Type 1 (DM1) is a complex, inherited disorder characterized by significant clinical heterogeneity, affecting multiple organ systems with varying severity and age of onset. It is a multisystemic disorder with a wide range of clinical presentations that lead to symptoms and complications associated with various body systems. Predicting the overall phenotype and prognosis is challenging due to the lack of a single determining factor, complicating medical management and clinical trials. While extensive research has explored the genetic and molecular mechanisms of DM1, the influence of gender on disease manifestations, progression, and outcomes remains elusive. Emerging evidence suggests that male patients often experience greater morbidity and mortality with severe muscular, cardiac, central nervous system, and respiratory impairments, while females are more prone to ophthalmological, gastrointestinal, and endocrine complications. Potential gender-based differences in inheritance patterns also require further investigation. Despite these disparities, gender-specific considerations are largely absent in clinical management and research, limiting the development of targeted therapeutic strategies. This review provides a comprehensive analysis of gender-related differences in DM1, emphasizing their implications for disease prognosis, diagnosis, and treatment. Recognizing gender as a crucial factor in DM1 research and clinical practice could improve patient outcomes and more personalized therapeutic approaches.

Myotonic dystrophies: an update on clinical features, molecular mechanisms, management, and gene therapy

Myotonic dystrophies (DM) encompass a group of complex genetic disorders characterized by progressive muscle weakness with myotonia and multisystemic involvement. The aim of our paper is to synthesize key findings and advancements in the understanding of DM, and to underline the multidisciplinary approach to DM, emphasizing the importance of genetic counseling, comprehensive clinical care, and symptom management. We discuss the genetic basis of DM, emphasizing the role of repeat expansions in disease pathogenesis, as well as cellular and animal models utilized for studying DM mechanisms and testing potential therapies. Diagnostic challenges, such as determining the size of disease expansions and assessing mosaicism, are elucidated alongside emerging genetic testing methods. Therapeutic strategies, mainly for DM1, are also explored, encompassing small molecules, nucleic acid-based therapies (NATs), and genome/transcriptome engineering. The challenges of such a therapeutic delivery and immunogenic response and the importance of innovative strategies, including viral vectors and AAV serotypes, are highlighted within the text. While no curative treatments have been approved, supportive and palliative care remains essential, with a focus on addressing multisystemic complications and maintaining functional independence. Continued exploration of these therapeutic advancements offers hope for comprehensive disease management and potentially curative therapies for DM1 and related disorders.

Fetal Brain MRI Findings in Myotonic Dystrophy and Considerations for Prenatal Genetic Testing

Background

Congenital myotonic dystrophy type 1 (DM1) is a rare congenital neuromuscular disorder associated with high morbidity and potential early mortality requiring lifelong symptomatic management. Prenatal presentations of DM1 have been associated with nonspecific ultrasound findings such as clubbed foot, polyhydramnios, ventriculomegaly, and decreased fetal movement, but many cases of DM1 have no ultrasound anomalies.

Methods

We sought to compare the clinical course and prenatal imaging findings in two cases of DM1 using retrospective chart review.

Results

This report demonstrates potential expansion of the prenatal phenotype of DM1 including fetal SVT and frontal bossing. Both cases shared unique prenatal imaging features of lateral ventricle dilation involving the anterior bodies and frontal horns on fetal MRI.

Discussion

Because congenital DM1 is most often maternally inherited, attention to maternal symptoms, physical examination, and family history can be helpful in recognizing cases. Molecular diagnosis of DM1 requires specialized testing of the 3' untranslated region of the DMPK gene, and DM1 will not be detected by current standard prenatal genetic testing with microarray, karyotype, or exome sequencing.

Hereditary Neuromuscular Disorders in Reproductive Medicine

Neuromuscular disorders (NMDs) encompass a broad range of hereditary and acquired conditions that affect motor units, significantly impacting patients' quality of life and reproductive health. This narrative review aims to explore in detail the reproductive challenges associated with major hereditary NMDs, including Charcot-Marie-Tooth disease (CMT), dystrophinopathies, Myotonic Dystrophy (DM), Facioscapulohumeral Muscular Dystrophy (FSHD), Spinal Muscular Atrophy (SMA), Limb-Girdle Muscular Dystrophy (LGMD), and Amyotrophic Lateral Sclerosis (ALS). Specifically, it discusses the stages of diagnosis and genetic testing, recurrence risk estimation, options for preimplantation genetic testing (PGT) and prenatal diagnosis (PND), the reciprocal influence between pregnancy and disease, potential obstetric complications, and risks to the newborn.

Nuclear envelope transmembrane proteins involved in genome organization are misregulated in myotonic dystrophy type 1 muscle

Myotonic dystrophy type 1 is a multisystemic disorder with predominant muscle and neurological involvement. Despite a well described pathomechanism, which is primarily a global missplicing due to sequestration of RNA-binding proteins, there are still many unsolved questions. One such question is the disease etiology in the different affected tissues. We observed alterations at the nuclear envelope in primary muscle cell cultures before. This led us to reanalyze a published RNA-sequencing dataset of DM1 and control muscle biopsies regarding the misregulation of NE proteins. We could identify several muscle NE protein encoding genes to be misregulated depending on the severity of the muscle phenotype. Among these misregulated genes were NE transmembrane proteins (NETs) involved in nuclear-cytoskeletal coupling as well as genome organization. For selected genes, we could confirm that observed gene-misregulation led to protein expression changes. Furthermore, we investigated if genes known to be under expression-regulation by genome organization NETs were also misregulated in DM1 biopsies, which revealed that misregulation of two NETs alone is likely responsible for differential expression of about 10% of all genes being differentially expressed in DM1. Notably, the majority of NETs identified here to be misregulated in DM1 muscle are mutated in Emery-Dreifuss muscular dystrophy or clinical similar muscular dystrophies, suggesting a broader similarity on the molecular level for muscular dystrophies than anticipated. This shows not only the importance of muscle NETs in muscle health and disease, but also highlights the importance of the NE in DM1 disease progression.

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.

Asymmetric inheritance of RNA toxicity in C. elegans expressing CTG repeats

Nucleotide repeat expansions are a hallmark of over 40 neurodegenerative diseases and cause RNA toxicity and multisystemic symptoms that worsen with age. Through an unclear mechanism, RNA toxicity can trigger severe disease manifestation in infants if the repeats are inherited from their mother. Here we use Caenorhabditis elegans bearing expanded CUG repeats to show that this asymmetric intergenerational inheritance of toxicity contributes to disease pathogenesis. In addition, we show that this mechanism is dependent on small RNA pathways with maternal repeat-derived small RNAs causing transcriptomic changes in the offspring, reduced motility, and shortened lifespan. We rescued the toxicity phenotypes in the offspring by perturbing the RNAi machinery in the affected hermaphrodites. This points to a novel mechanism linking maternal bias and the RNAi machinery and suggests that toxic RNA is transmitted to offspring, causing disease phenotypes through intergenerational epigenetic inheritance.

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Maternal origin of expanded CUG repeats induces RNA toxicity in Caenorhabditis elegans offspring

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Offspring of affected hermaphrodites show molecular and phenotypic disease phenotypes

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The RNAi machinery is directly related to the maternal inheritance of RNA toxicity

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Altering the RNAi machinery in affected hermaphrodites rescues toxicity in offspring

Current Status of Genetic Counselling for Rare Diseases in Spain

Genetic Counselling is essential for providing personalised information and support to patients with Rare Diseases (RD). Unlike most other developed countries, Spain does not recognize geneticists or genetic counsellors as healthcare professionals Thus, patients with RD face not only challenges associated with their own disease but also deal with lack of knowledge, uncertainty, and other psychosocial issues arising as a consequence of diagnostic delay. In this review, we highlight the importance of genetic counsellors in the field of RD as well as evaluate the current situation in which rare disease patients receive genetic services in Spain. We describe the main units and strategies at the national level assisting patients with RD and we conclude with a series of future perspectives and unmet needs that Spain should overcome to improve the management of patients with RD.

Transcriptome Analysis in a Primary Human Muscle Cell Differentiation Model for Myotonic Dystrophy Type 1

Myotonic dystrophy type 1 (DM1) is caused by CTG-repeat expansions leading to a complex pathology with a multisystemic phenotype that primarily affects the muscles and brain. Despite a multitude of information, especially on the alternative splicing of several genes involved in the pathology, information about additional factors contributing to the disease development is still lacking. We performed RNAseq and gene expression analyses on proliferating primary human myoblasts and differentiated myotubes. GO-term analysis indicates that in myoblasts and myotubes, different molecular pathologies are involved in the development of the muscular phenotype. Gene set enrichment for splicing reveals the likelihood of whole, differentiation stage specific, splicing complexes that are misregulated in DM1. These data add complexity to the alternative splicing phenotype and we predict that it will be of high importance for therapeutic interventions to target not only mature muscle, but also satellite cells.

Lesion distribution and substrate of white matter damage in myotonic dystrophy type 1: Comparison with multiple sclerosis

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The supratentorial distribution of lesions is similar in DM1 and MS.

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Patients with DM1 do not show infratentorial lesions.

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Quantitative magnetization transfer supports the presence of demyelination in DM1 lesions, but not in the NAWM.

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Anterior temporal lobe lesions in DM1 might have a different substrate than periventricular ones.

Myotonic Dystrophy type 1 (DM1) is an autosomal dominant condition caused by expansion of the CTG triplet repeats within the myotonic dystrophy protein of the kinase (DMPK) gene. The central nervous system is involved in the disease, with multiple symptoms including cognitive impairment. A typical feature of DM1 is the presence of widespread white matter (WM) lesions, whose total volume is associated with CTG triplet expansion. The aim of this study was to characterize the distribution and pathological substrate of these lesions as well as the normal appearing WM (NAWM) using quantitative magnetization transfer (qMT) MRI, and comparing data from DM1 patients with those from patients with multiple sclerosis (MS). Twenty-eight patients with DM1, 29 patients with relapsing-remitting MS, and 15 healthy controls had an MRI scan, including conventional and qMT imaging. The average pool size ratio (F), a proxy of myelination, was computed within lesions and NAWM for every participant. The lesion masks were warped into MNI space and lesion probability maps were obtained for each patient group. The lesion distribution, total lesion load and the tissue-specific mean F were compared between groups. The supratentorial distribution of lesions was similar in the 2 patient groups, although mean lesion volume was higher in MS than DM1. DM1 presented higher prevalence of anterior temporal lobe lesions, but none in the cerebellum and brainstem. Significantly reduced F values were found within DM1 lesions, suggesting a loss of myelin density. While F was reduced in the NAWM of MS patients, it did not differ between DM1 and controls. Our results provide further evidence for a need to compare histology and imaging using new MRI techniques in DM1 patients, in order to further our understanding of the underlying disease process contributing to WM disease.

Myotonic Dystrophy-A Progeroid Disease?

Myotonic dystrophies (DM) are slowly progressing multisystemic disorders caused by repeat expansions in the DMPK or CNBP genes. The multisystemic involvement in DM patients often reflects the appearance of accelerated aging. This is partly due to visible features such as cataracts, muscle weakness, and frontal baldness, but there are also less obvious features like cardiac arrhythmia, diabetes or hypogammaglobulinemia. These aging features suggest the hypothesis that DM could be a segmental progeroid disease. To identify the molecular cause of this characteristic appearance of accelerated aging we compare clinical features of DM to “typical” segmental progeroid disorders caused by mutations in DNA repair or nuclear envelope proteins. Furthermore, we characterize if this premature aging effect is also reflected on the cellular level in DM and investigate overlaps with “classical” progeroid disorders. To investigate the molecular similarities at the cellular level we use primary DM and control cell lines. This analysis reveals many similarities to progeroid syndromes linked to the nuclear envelope. Our comparison on both clinical and molecular levels argues for qualification of DM as a segmental progeroid disorder.

Myotonic Dystrophy and Developmental Regulation of RNA Processing

Myotonic dystrophy (DM) is a multisystemic disorder caused by microsatellite expansion mutations in two unrelated genes leading to similar, yet distinct, diseases. DM disease presentation is highly variable and distinguished by differences in age-of-onset and symptom severity. In the most severe form, DM presents with congenital onset and profound developmental defects. At the molecular level, DM pathogenesis is characterized by a toxic RNA gain-of-function mechanism that involves the transcription of noncoding microsatellite expansions. These mutant RNAs disrupt key cellular pathways, including RNA processing, localization, and translation. In DM, these toxic RNA effects are predominantly mediated through the modulation of the muscleblind-like and CUGBP and ETR-3-like factor families of RNA binding proteins (RBPs). Dysfunction of these RBPs results in widespread RNA processing defects culminating in the expression of developmentally inappropriate protein isoforms in adult tissues. The tissue that is the focus of this review, skeletal muscle, is particularly sensitive to mutant RNA-responsive perturbations, as patients display a variety of developmental, structural, and functional defects in muscle. Here, we provide a comprehensive overview of DM1 and DM2 clinical presentation and pathology as well as the underlying cellular and molecular defects associated with DM disease onset and progression. Additionally, fundamental aspects of skeletal muscle development altered in DM are highlighted together with ongoing and potential therapeutic avenues to treat this muscular dystrophy. © 2018 American Physiological Society. Compr Physiol 8:509-553, 2018.

Physical function and mobility in children with congenital myotonic dystrophy

INTRODUCTION

Congenital myotonic dystrophy (CDM) occurs when symptoms of myotonic dystrophy present at birth. In this study we evaluated the relationship between physical function, muscle mass, and age to provide an assessment of the disease and help prepare for therapeutic trials.

METHODS

CDM participants performed timed functional tests (TFTs), the first 2 minutes of 6-minute walk tests (2/6MWTs), and myometry tests, and also performed dual-energy X-ray absorption (DEXA) scans. Healthy controls (HCs) performed TFTs, 6MWTs, and myometry.

RESULTS

Thirty-seven children with CDM and 27 HCs (age range 3-13 years) participated in the study. There were significant differences in the 10-meter walk (11.3 seconds in CDM vs. 6.8 seconds in HC) and 2MWT (91 meters in CDM vs. 193 meters in HCs). DEXA lean mass of the right arm correlated with grip strength (r = 0.91), and lean mass of the right leg correlated with 6MWT (r = 0.62).

CONCLUSION

Children with CDM have significant limitations in strength and mobility. The tests performed were reliable, and lean muscle mass may serve as a useful biomarker. Muscle Nerve 56: 224-229, 2017.

Prenatal diagnosis of congenital myopathies and muscular dystrophies

Congenital myopathies and muscular dystrophies constitute a genetically and phenotypically heterogeneous group of rare inherited diseases characterized by muscle weakness and atrophy, motor delay and respiratory insufficiency. To date, curative care is not available for these diseases, which may severely affect both life-span and quality of life. We discuss prenatal diagnosis and genetic counseling for families at risk, as well as diagnostic possibilities in sporadic cases.

Congenital and childhood myotonic dystrophy: Current aspects of disease and future directions

Myotonic dystrophy type 1 (DM1) is multisystem disease arising from mutant CTG expansion in the non-translating region of the dystrophia myotonica protein kinase gene. While DM1 is the most common adult muscular dystrophy, with a worldwide prevalence of one in eight thousand, age of onset varies from before birth to adulthood. There is a broad spectrum of clinical severity, ranging from mild to severe, which correlates with number of DNA repeats. Importantly, the early clinical manifestations and management in congenital and childhood DM1 differ from classic adult DM1. In neonates and children, DM1 predominantly affects muscle strength, cognition, respiratory, central nervous and gastrointestinal systems. Sleep disorders are often under recognised yet a significant morbidity. No effective disease modifying treatment is currently available and neonates and children with DM1 may experience severe physical and intellectual disability, which may be life limiting in the most severe forms. Management is currently supportive, incorporating regular surveillance and treatment of manifestations. Novel therapies, which target the gene and the pathogenic mechanism of abnormal splicing are emerging. Genetic counselling is critical in this autosomal dominant genetic disease with variable penetrance and potential maternal anticipation, as is assisting with family planning and undertaking cascade testing to instigate health surveillance in affected family members. This review incorporates discussion of the clinical manifestations and management of congenital and childhood DM1, with a particular focus on hypersomnolence and sleep disorders. In addition, the molecular genetics, mechanisms of disease pathogenesis and development of novel treatment strategies in DM1 will be summarised.

Myotonic dystrophy

Myotonic dystrophy (dystrophia myotonica, DM) is one of the most common lethal monogenic disorders in populations of European descent. DM type 1 was first described over a century ago. More recently, a second form of the disease, DM type 2 was recognized, which results from repeat expansion in a different gene. Both disorders have autosomal dominant inheritance and multisystem features, including myotonic myopathy, cataract, and cardiac conduction disease. This article reviews the clinical presentation and pathophysiology of DM and discusses current management and future potential for developing targeted therapies.

Muscular myopathies other than myotonic dystrophy also associated with (CTG)n expansion at the DMPK locus

Objective:

Assess triplet repeat expansion (CTG)_n at the ‘dystrophia-myotonica protein kinase’ (DMPK) locus in muscular myopathies to elucidate its role in myopathic symptoms and enable genetic counseling and prenatal diagnosis in families.

Methods and Results:

Individuals with symptoms of myopathy, hypotonia and controls selected randomly from the population were evaluated for triplet repeat expansion of (CTG)_n repeats in the 3’untranslated region (UTR) of DMPK gene, the causative mutation in myotonic dystrophy (DM). DNA was isolated from peripheral blood of 40 individuals; they presented symptoms of muscle myopathy (n = 11), muscle hypotonia (n = 4), members of their families (n = 5) and control individuals from random population (n = 20). Molecular analysis of genomic DNA by polymerase chain reaction (PCR) using primers specific for the DMPK gene encompassing the triplet repeat expansion, showed that all controls (n = 20) gave a 2.1 kb band indicating normal triplet repeat number. Three out of 11 cases (two clinically diagnosed DM and one muscular dystrophy) had an expansion of the (CTG)_n repeat in the range of 1000-2100 repeats corresponding to the repeat number in cases of severe DM. Other two of these 11 cases, showed a mild expansion of ~ 66 repeats. Three samples, which included two cases of hypotonia and the father of a subject with muscular dystrophy, also gave a similar repeat expansion (~66 repeats).

Conclusion:

Results suggest a role of (CTG)_n expansion at the DMPK locus in unexplained hypotonias and muscular myopathies other than DM. This calls for screening of the triplet repeat expansion at the DMPK locus in cases of idiopathic myopathies and hypotonia.

Enhanced aggregation of androgen receptor in induced pluripotent stem cell-derived neurons from spinal and bulbar muscular atrophy

Spinal and bulbar muscular atrophy (SBMA) is an X-linked motor neuron disease caused by a CAG repeat expansion in the androgen receptor (AR) gene. Ligand-dependent nuclear accumulation of mutant AR protein is a critical characteristic of the pathogenesis of SBMA. SBMA has been modeled in AR-overexpressing animals, but precisely how the polyglutamine (polyQ) expansion leads to neurodegeneration is unclear. Induced pluripotent stem cells (iPSCs) are a new technology that can be used to model human diseases, study pathogenic mechanisms, and develop novel drugs. We established SBMA patient-derived iPSCs, investigated their cellular biochemical characteristics, and found that SBMA-iPSCs can differentiate into motor neurons. The CAG repeat numbers in the AR gene of SBMA-iPSCs and also in the atrophin-1 gene of iPSCs derived from another polyQ disease, dentato-rubro-pallido-luysian atrophy (DRPLA), remain unchanged during reprogramming, long term passage, and differentiation, indicating that polyQ disease-associated CAG repeats are stable during maintenance of iPSCs. The level of AR expression is up-regulated by neuronal differentiation and treatment with the AR ligand dihydrotestosterone. Filter retardation assays indicated that aggregation of ARs following dihydrotestosterone treatment in neurons derived from SBMA-iPSCs increases significantly compared with neurological control iPSCs, easily recapitulating the pathological feature of mutant ARs in SBMA-iPSCs. This phenomenon was not observed in iPSCs and fibroblasts, thereby showing the neuron-dominant phenotype of this disease. Furthermore, the HSP90 inhibitor 17-allylaminogeldanamycin sharply decreased the level of aggregated AR in neurons derived from SBMA-iPSCs, indicating a potential for discovery and validation of candidate drugs. We found that SBMA-iPSCs possess disease-specific biochemical features and could thus open new avenues of research into not only SBMA, but also other polyglutamine diseases.

Is there a Mendelian transmission ratio distortion of the c.429_452dup(24bp) polyalanine tract ARX mutation?

Intellectual disability is common. Aristaless-related homeobox (ARX) gene is one of the most frequently mutated and pleiotropic genes, implicated in 10 different phenotypes. More than half of ~100 reported cases with ARX mutations are due to a recurrent duplication of 24 bp, c.429_452dup, which leads to polyalanine tract expansion. The excess of affected males among the offspring of the obligate carrier females raised the possibility of transmission ratio distortion for the c.429_452dup mutation. We found a significant deviation from the expected Mendelian 1:1 ratio of transmission in favour of the c.429_452dup ARX mutation. We hypothesise that the preferential transmission of the c.429_452dup mutation may be due to asymmetry of meiosis in the oocyte. Our findings may have implications for genetic counselling of families segregating the c.429_452dup mutation and allude to putative role of ARX in oocyte biology.

Cartilage-hair hypoplasia caused by novel compound heterozygous RMRP mutations

Cartilage-hair hypoplasia is a rare, autosomal recessive skeletal dysplasia, caused by mutations in the RMRP gene. The skeletal abnormalities include irregular metaphyses and cone shaped epiphyses of the hands. Molecular diagnosis confirmed two novel RMRP mutations in a compound heterozygous state in two siblings with this condition.

Myotonic dystrophy types 1 and 2

Myotonic dystrophies (dystrophia myotonica, or DM) are inherited disorders characterized by myotonia and progressive muscle degeneration, which are variably associated with a multisystemic phenotype. To date, two types of myotonic dystrophy, type 1 (DM1) and type 2 (DM2), are known to exist; both are autosomal dominant disorders caused by expansion of an untranslated short tandem repeat DNA sequence (CTG)(n) and (CCTG)(n), respectively. These expanded repeats in DM1 and DM2 show different patterns of repeat-size instability. Phenotypes of DM1 and DM2 are similar but there are some important differences, most conspicuously in the severity of the disease (including the presence or absence of the congenital form), muscles primarily affected (distal versus proximal), involved muscle fiber types (type 1 versus type 2 fibers), and some associated multisystemic phenotypes. The pathogenic mechanism of DM1 and DM2 is thought to be mediated by the mutant RNA transcripts containing expanded CUG and CCUG repeats. Strong evidence supports the hypothesis that sequestration of muscle-blind like (MBNL) proteins by these expanded repeats leads to misregulated splicing of many gene transcripts in corroboration with the raised level of CUG-binding protein 1. However, additional mechanisms, such as changes in the chromatin structure involving CTCN-binding site and gene expression dysregulations, are emerging. Although treatment of DM1 and DM2 is currently limited to supportive therapies, new therapeutic approaches based on pathogenic mechanisms may become feasible in the near future.

Preimplantation genetic diagnosis for myotonic dystrophy type 1: upon request to child

Preimplantation genetic diagnosis (PGD) is an alternative to prenatal diagnosis for patients at risk of transmitting an inherited disease such as myotonic dystrophy type 1(DM1) to their offspring. In this paper, the clinical application of preimplantation diagnosis for DM1 upon request to children born is described in a large cohort of risk couples. PGD could be offered to all 78 couples opting for PGD regardless of the triplet repeat size. The incidence of major complications was minimalised following a careful assessment in affected DM1 females anticipating possible cardiological, obstetrical and anaesthetical problems. A live-birth delivery rate per cycle with oocyte retrieval of 20% was the outcome. Forty-eight of the 49 children born are in good health and have normal psychomotor development.

Preimplantation genetic diagnosis for myotonic dystrophy type 1 in the UK

Myotonic dystrophy type 1 (DM1) is a dominant multisystemic disorder caused by expansion of a trinucleotide repeat in a non-coding region of DMPK. Prenatal diagnosis (PND) is available; however, the decision to terminate affected pregnancies is difficult as the extent of disability is hard to predict from the size of the expansion. In preimplantation genetic diagnosis (PGD) genetic analysis is carried out before the establishment of pregnancy. This paper reviews the largest number of cycles of PGD for DM1 in the UK indicating that PGD is a practical option for affected couples.