Clinical characteristics of pregnancies complicated by congenital myotonic dystrophy

Parental diagnostic delay and developmental outcomes in congenital and childhood-onset myotonic dystrophy type 1

AIM

To investigate the timing of type 1 myotonic dystrophy (DM1) diagnosis in parents of affected children and describe children's perinatal characteristics and developmental outcomes.

METHOD

This was a descriptive case series of children with congenital myotonic dystrophy (CDM) and childhood-onset myotonic dystrophy (ChDM). Parental timing of DM1 diagnosis and the perinatal, motor, and cognitive outcomes of paediatric patients were recorded.

RESULTS

A total of 139 children followed by 12 highly specialized tertiary care neuromuscular centres in Italy and one tertiary neuromuscular centre in the USA were included: 105 children with CDM and 34 children with ChDM (mean age 8 years 8 months and 12 years 2 months respectively; 49 males and 17 males respectively). Seventy (50%) parents were diagnosed with adult-onset DM1 after the affected child was diagnosed. Only 12 (17%) of the 69 parents known to be affected had prenatal testing. Of the 105 children with CDM, 98% had maternally inherited CDM, 36% were born preterm, 83% required a stay in the neonatal intensive care unit for more than 48 hours, 84% and 79% had ambulation and speech delay, and 84% had an IQ lower than 70. Of the 34 children with ChDM, 59% had paternally inherited ChDM, 91% were born at term, and 36% had an IQ lower than 70.

INTERPRETATION

Delay in diagnosing DM1 affects family planning. The prenatal and perinatal outcomes of the affected offspring emphasize the need for proactive counselling as parents may be reluctant to conduct prenatal testing.

Maternal health and obstetric complications of genetic neuromuscular disorders in pregnancy: A systematic review

BACKGROUND

Genetic neuromuscular disorders affect muscle function and control by the nervous system, presenting significant clinical challenges, particularly during pregnancy.

OBJECTIVES

To systematically review the literature on the obstetric outcomes and complications in women with genetic neuromuscular disorders.

SEARCH STRATEGY

We searched PubMed/Medline, Scopus, and CINAHL Ultimate from inception till June 2024 using terms like "pregnancy", "genetic neuromuscular disorder", "myotonic dystrophy", "maternal health" etc. SELECTION CRITERIA: Pregnant women with genetic neuromuscular disorders.

DATA COLLECTION AND ANALYSIS

Screening, selection, and data extraction were performed independently by two reviewers.

MAIN RESULTS

A total of 28 studies from 1978 to 2023 examined pregnancy outcomes in women with genetic neuromuscular disorders. The disorders included myotonic dystrophy, spinal muscular atrophy (SMA), Charcot-Marie-Tooth disease (CMT), and others. Common complications were polyhydramnios, preterm labor, miscarriages, and cesarean sections. Myotonic dystrophy type 1 (DM1) showed higher neonatal risks than type 2 (DM2). Women with SMA faced exacerbated muscle weakness, while CMT and limb-girdle muscular dystrophy were associated with preterm labor and cesarean deliveries. Pompe disease exacerbated symptoms, and GNE myopathy showed similar pregnancy outcomes to the general population. Non-dystrophic myotonias had higher fetal distress and postpartum complications.

CONCLUSIONS

Women with genetic neuromuscular disorders face increased pregnancy complications, including preterm labor, cesarean sections, and disease symptom exacerbation. Multidisciplinary care between neurologists and obstetricians is essential in managing these high-risk pregnancies effectively, ensuring better maternal and neonatal outcomes. Further research is needed to develop standardized care protocols and improve clinical management.

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.

Case report of congenital myotonic dystrophy with multiple prenatal sonographic findings

Objectives

Myotonic dystrophy 1 (DM1) is an autosomal dominant inherited neuromuscular disorder. The most severe form is congenital myotonic dystrophy (cDM). Prenatal diagnosis is complicated and sonographic findings of cDM that are not pathognomonic occur in the late second or early third trimester of pregnancy.

Case presentation

It is the case of prenatally diagnosed cDM. In 32 weeks of pregnancy multiple sonographic findings such as severe polyhydramnios, bilateral talipes, fetal legs akinesia, macrocephaly with mild bilateral ventriculomegaly, right-sided pleural effusion and diaphragmatic pathology were observed by fetal medicine specialist. As the patient complained of weakness in her limbs, she was consulted by a neurologist. The neurological examination revealed a pathognomonic sign of DM1 - grip myotonia. The amniotic fluid and the mother's blood sample were further tested for DM1. This identified >150 repeats in one copy of the DMPK gene of the both, which is consistent with the diagnosis DM1.

Conclusions

The sonographic findings of fetal limb abnormalities with progressive polyhydramnios is an indication for maternal neurological examination and genetic testing due to myotonic dystrophy.

Congenital hypotonia: systematic approach for prenatal detection

OBJECTIVES

Congenital hypotonic conditions are rare and heterogeneous, and some are severely debilitating or lethal. Contrary to its prominent postnatal manifestation, the prenatal presentation of hypotonia is frequently subtle, inhibiting prenatal detection. We aimed to characterize the prenatal sonographic manifestation of congenital hypotonia throughout pregnancy, evaluate the yield of diagnostic tests and propose diagnostic models to increase its prenatal detection.

METHODS

This was a retrospective observational study of singleton pregnancies with congenital hypotonia, diagnosed either prenatally or immediately after birth, at a single tertiary center between the years 2012 and 2020. Prenatally, hypotonia was diagnosed if a fetus showed sonographic or clinical signs suggestive of hypotonia and had a confirmed underlying genetic condition, or in the absence of a known genetic abnormality if the fetus exhibited multiple prominent signs suggestive of hypotonia. Postnatally, it was diagnosed in neonates displaying reduced muscle tone leading to reduced spontaneous movement, reduced swallowing or feeding difficulty. We reviewed the medical records of pregnant patients carrying fetuses subsequently diagnosed with congenital hypotonia and assessed the yield of ultrasound scans, fetal magnetic resonance imaging, computed tomography and genetic tests. The detection rate of sonographic signs suggesting fetal hypotonia was calculated. The prevalence of non-specific signs, including polyhydramnios, persistent breech presentation, intrauterine growth restriction and maternal perception of reduced fetal movement, were compared between the study group and the local liveborn singleton population. Potential detection rates of different theoretical semiotic diagnostic models, differing in the threshold for referral for a targeted scan, were assessed based on the cohort's data.

RESULTS

The study group comprised 26 cases of congenital hypotonia, of which 10 (38.5%) were diagnosed prenatally, and the controls included 95 105 singleton live births, giving a prevalence of congenital hypotonia of 1:3658. Nuchal translucency thickness and the early anomaly scan at 13-17 weeks were normal in all 22 and 23 cases, respectively, in which this was performed. The mid-trimester scan performed at 19-25 weeks was abnormal in four of 24 (16.7%) cases. The overall prenatal detection rate of congenital hypotonic conditions in our cohort was 38.5%. Only cases which underwent a targeted scan were detected and, among the 16 cases which underwent this scan, the prenatal detection rate was 62.5% compared with 0% in pregnancies that did not undergo this scan (P = 0.003). An abnormal genetic diagnosis was obtained in 21 (80.8%) cases using the following modalities: chromosomal microarray analysis (CMA) in two (9.5%), whole-exome sequencing (WES) in 14 (66.7%) and methylation analysis in five (23.8%). CMA was abnormal in 8% (2/25) of the cases and WES detected a causative genetic mutation in 87.5% (14/16) of the cases in which these were performed. Comparison of non-specific signs in the study group with those in the local singleton population showed that hypotonic fetuses had significantly more polyhydramnios (64.0% vs 3.0%, P < 0.0001), persistent breech presentation (58.3% vs 4.2%, P < 0.0001), intrauterine growth restriction (30.8% vs 3.0%, P < 0.0001) and maternal perception of reduced fetal movement (32.0% vs 4.7%, P < 0.0001). Prenatally, the most commonly detected signs supporting a diagnosis of hypotonia were structural anomaly (62.5%, 10/16), reduced fetal movement (46.7%, 7/15), joint contractures (46.7%, 7/15) and undescended testes ≥ 30 weeks (42.9%, 3/7 males). Proposed diagnostic strategies that involved performing a targeted scan for a single non-specific ultrasound sign or two such signs, and then carrying out a comprehensive genetic evaluation for any additional sign, offered theoretical detection rates in our cohort of 88.5% and 57.7%, respectively.

CONCLUSIONS

Congenital hypotonic conditions are rare and infrequently detected prenatally. Sonographic signs are visible from the late second trimester. A targeted scan increases prenatal detection significantly. Comprehensive genetic testing, especially WES, is the cornerstone of diagnosis in congenital hypotonia. Theoretical diagnostic models which may increase prenatal detection are provided. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Infection-Induced Rhabdomyolysis in a Pregnant Woman with Undiagnosed Myotonic Dystrophy: A Case Report

A 34-year-old nulliparous gravid female presented with acute bilateral pyelonephritis at 29 + 5 weeks gestation. The patient was relatively well until two weeks ago when a slight increase in amniotic fluid was noted. Further investigation revealed myoglobinuria and significantly elevated levels of creatine phosphokinase. The patient was subsequently diagnosed with rhabdomyolysis. Twelve hours after admission, the patient noted reduced fetal movements. A non-stress test revealed fetal bradycardia and non-reassuring variability in fetal heart rate. An emergency cesarean section was performed, and a "floppy" female child was delivered. Genetic testing revealed congenital myotonic dystrophy, and the mother was also diagnosed with myotonic dystrophy. Rhabdomyolysis has a very low incidence in pregnancy. Herein, we report a rare case of myotonic dystrophy with rhabdomyolysis in a gravid female with no history of myotonic dystrophy. Acute pyelonephritis is a causative agent of rhabdomyolysis that results in preterm birth.

Congenital Myotonic Dystrophy: An Overlooked Diagnosis Not Amenable to Detection by Sequencing

OBJECTIVE

To increase the clinical awareness of the need for genetic evaluation for congenital myotonic dystrophy in cases of fetal akinesia sequence and idiopathic polyhydramnios.

METHODS

Retrospective case review.

RESULT

A 27 y.o. G1P0 with no significant family history presented for ultrasound at 25 weeks gestation. Notable findings included lack of extension of the fetal arms and legs with bilateral talipes consistent with fetal akinesia sequence. Polyhydramnios with an amniotic fluid index of 32.2cm was also present. Amniotic fluid obtained by amniocentesis revealed normal results for a chromosomal microarray and a next generation sequencing panel for arthrogryposis. The patient underwent serial amnioreductions for recurrent severe polyhydramnios with removal of a total of 9.3 L. Further amniotic fluid testing for CDM1 identified >200 repeats in one copy of the fetal DMPK gene, consistent with a diagnosis of congenital myotonic dystrophy type 1. The patient was delivered at 35 weeks gestation and neonatal demise occurred on the second day of life.

CONCLUSION

Congenital myotonic dystrophy should be a consideration for cases of severe polyhydramnios identified on ultrasound. Myotonic dystrophy is detected using PCR and southern blot and is not typically included on next generation sequencing panels that test for similar conditions. This article is protected by copyright. All rights reserved.

Deciphering the mechanisms underlying brain alterations and cognitive impairment in congenital myotonic dystrophy

Myotonic dystrophy type 1 (DM1) is a multisystemic and heterogeneous disorder caused by the expansion of CTG repeats in the 3' UTR of the myotonic dystrophy protein kinase (DMPK) gene. There is a congenital form (CDM1) of the disease characterized by severe hypotonia, respiratory insufficiency as well as developmental delays and intellectual disabilities. CDM1 infants manifest important brain structure abnormalities present from birth while, in contrast, older patients with adult-onset DM1 often present neurodegenerative features and milder progressive cognitive deficits. Promising therapies targeting central molecular mechanisms contributing to the symptoms of adult-onset DM1 are currently in development, but their relevance for treating cognitive impairment in CDM1, which seems to be a partially distinct neurodevelopmental disorder, remain to be elucidated. Here, we provide an update on the clinical presentation of CDM1 and review recent in vitro and in vivo models that have provided meaningful insights on its consequences in development, with a particular focus on the brain. We discuss how enhanced toxic gain-of-function of the mutated DMPK transcripts with larger CUG repeats and the resulting dysregulation of RNA-binding proteins may affect the developing cortex in utero. Because the methylation of CpG islets flanking the trinucleotide repeats has emerged as a strong biomarker of CDM1, we highlight the need to investigate the tissue-specific impacts of these chromatin modifications in the brain. Finally, we outline promising potential therapeutic treatments for CDM1 and propose future in vitro and in vivo models with great potential to shed light on this disease.

Chylothorax as a complication of congenital myotonic dystrophy: A retrospective cohort study

BACKGROUND

The association between congenital myotonic dystrophy (CMD) and chylothorax is poorly recognized.

AIMS

To evaluate the proportion of chylothorax in infants with CMD compared to its prevalence in infants without CMD.

STUDY DESIGN

Single-center, retrospective, cohort study.

SUBJECTS

Infants managed at a neonatal intensive care unit from 2003 to 2019.

OUTCOME MEASURES

CMD was diagnosed using Southern blot for the quantification of CTG repeats in the dystrophia myotonica protein kinase (DMPK) gene. Prenatal and postnatal data of eligible infants with CMD were collected from the patients' medical records. The primary outcome was the proportion of chylothorax.

RESULTS

While the proportion of chylothorax in eligible infants without CMD was 0.25% (27/10714), that in infants with CMD was 50% (5/10; odds ratio (OR), 386.3; 95% confidence interval (CI), 84.4-1850.8; P < 0.001). The variables that were significantly different between infants with CMD with chylothorax and those without chylothorax were as follows: maternal age (33.0 vs. 24.8; P = 0.005), polyhydramnios (5/5 vs 1/5; P = 0.034), number of CTG repeats (1980 vs. 1500; P = 0.038), duration of invasive mechanical ventilation (220 vs. 2, P = 0.009), and duration of hospitalization (217.2 vs 68.0; P = 0.014). The mortality rate of all eligible infants with CMD was 5/10 (50%). No variables were significantly associated with mortality.

CONCLUSIONS

The proportion of chylothorax in infants with CMD was significantly higher than that in infants without CMD. Furthermore, the proportion was higher than that reported in previous studies on congenital chylothorax. This suggests that chylothorax may be frequently experienced in the clinical course of CMD.

Genetics of recurrent pregnancy loss: a review

PURPOSE OF REVIEW

Human reproduction is remarkably inefficient; with pregnancy loss occurring in 10-30% of clinically recognized pregnancies. Of those, 3-5% of couples experience recurrent pregnancy loss (RPL), more than 50% of who never receive an underlying diagnosis. Herein, we review evidence that genetic changes, including pathogenic variant(s) in highly penetrant genes, may provide an explanation for a proportion of couples with pregnancy loss.

RECENT FINDINGS

Genetic abnormalities that may predispose to pregnancy loss include chromosomal aneuploidy, copy number variants, single-gene changes and others. Although previously limited by the need for hypothesis-driven assessment, advancement of various molecular technologies have sheparded in the opportunity to identify molecular cause of highly heterogeneous conditions, including RPL. The identification of causative genetic aberrations associated with RPL demonstrates a promising area of further research.

SUMMARY

The journey of human development from a single-cell zygote to a term infant is complex process. Early research into copy number variants and highly penetrant single-gene changes may provide diagnosis for a proportion of couples with RPL as well as inform genes critical for early human development.

Genetic diagnosis and clinical evaluation of severe fetal akinesia syndrome

Objective

In this retrospective study, we describe the clinical course, ultrasound findings and genetic investigations of fetuses affected by fetal akinesia.

Materials and Methods

We enrolled 22 eukaryotic fetuses of 18 families, diagnosed with fetal akinesia between 2008 and 2016 at the Department of Obstetrics and Feto‐Maternal Medicine at the Medical University of Vienna. Routine genetic evaluation included karyotyping and chromosomal microarray analysis. Retrospectively, exome sequencing was performed in the index case of 11 families, if stored DNA was available. Confirmation analyses and genetic diagnosis of siblings were performed by using Sanger sequencing.

Results

Whole exome sequencing identified pathogenic variants of CNTN1, RYR1, NEB, GLDN, HRAS and TNNT3 in six cases of 11 families. In three of these families, the variants were confirmed in the respective sibling.

Conclusions

The present study demonstrates a high diagnostic yield of exome sequencing in fetuses affected by akinesia syndrome, especially if family history is positive. Still, in a large part the underlying genetic cause remained unknown, whereas precise clinical evaluation in combination with exome sequencing shows to be the best tool to find the disease causing variants.

Impact of prematurity and the CTG repeat length on outcomes in congenital myotonic dystrophy

Objective

Patients with congenital myotonic dystrophy (CDM) tend to be born preterm. Although the CDM severity generally depends on the CTG repeat length, prematurity may also affect the prognosis in patients with CDM. Given that preterm birth is expected to increase the risk of CDM in newborns, we investigated the outcomes of newborns with CDM according to gestational age to assess prematurity and the CTG repeat length for predicting prognosis.

Results

We assessed the outcomes of 54 infants with CDM using data collected from our hospitals and previously published studies. The patients were divided into mild and severe groups based on clinical outcomes. Logistic regression analysis was performed to estimate odds ratios (ORs) for CDM prognosis according to gestational age and the CTG repeat length and to construct a predictive model. Logistic regression analysis showed both the CTG repeat and gestational age were significantly associated with severe outcomes in patients with CDM (OR: 32.27, 95% CI 3.45–300.7; p = 0.002 and OR: 0.73, 95% CI 0.58–0.93; p = 0.0094, respectively). This predictive model for CDM prognosis exhibited good sensitivity (63%) and specificity (86%). Both prematurity and the CTG repeat length were significantly associated with the CDM severity.

Myotonic disorders and pregnancy

Myotonic disorders represent significant risk in pregnancy due to their complexity and the risk of maternal and fetal complications. Care of these pregnancies requires detailed pre-conception counselling, close monitoring of mother and fetus during the pregnancy and a delivery and postpartum plan involving a multidisciplinary team approach. A case of a woman with myotonia congenita diagnosed in pregnancy is presented, the general principles of care of women with myotonic disorders discussed, and care of the specific conditions in pregnancy reviewed. Trial registration: Not applicable.