Myotonic Dystrophy Type 1

Clinical characteristics.

Myotonic dystrophy type 1 (DM1) is a multisystem disorder that affects skeletal and smooth muscle as well as the eye, heart, endocrine system, and central nervous system. The clinical findings, which span a continuum from mild to severe, have been categorized into three somewhat overlapping phenotypes: mild, classic, and congenital.

• Mild DM1 is characterized by cataract and mild myotonia (sustained muscle contraction); life span is normal.
• Classic DM1 is characterized by muscle weakness and wasting, myotonia, cataract, and often cardiac conduction abnormalities; adults may become physically disabled and may have a shortened life span.
• Congenital DM1 is characterized by hypotonia and severe generalized weakness at birth, often with respiratory insufficiency and early death; intellectual disability is common.

Diagnosis/testing.

DM1 is caused by expansion of a CTG trinucleotide repeat in the noncoding region of DMPK. The diagnosis of DM1 is suspected in individuals with characteristic muscle weakness and is confirmed by molecular genetic testing of DMPK. CTG repeat length exceeding 34 repeats is abnormal. Molecular genetic testing detects pathogenic variants in nearly 100% of affected individuals.

Management.

Treatment of manifestations: Use of ankle-foot orthoses, wheelchairs, or other assistive devices; special education support for affected children; treatment of hypothyroidism; management of pain; consultation with a cardiologist for symptoms or EKG evidence of arrhythmia; removal of cataracts if vision is impaired; hormone replacement therapy for males with hypogonadism; surgical excision of pilomatrixoma and basal cell carcinomas.

Prevention of secondary complications: Choice of induction agents, airway care, local anesthesia, and neuromuscular blockade to minimize complications during surgery; cardiac pacemakers or implantable cardioverter-defibrillators may prevent life-threatening arrhythmias; continue physical activity and maintain appropriate weight.

Surveillance: Annual EKG or 24-hour Holter monitoring; annual measurement of fasting serum glucose concentration and glycosylated hemoglobin concentration; ophthalmology examination every two years; attention to nutritional status; polysomnography for sleep disturbances.

Agents/circumstances to avoid: Cholesterol-lowering medications (i.e., statins), which can cause muscle pain and weakness; the anesthetic agent vecuronium; succinylcholine, propofol, and doxorubicin; smoking; obesity; illicit drug use; excessive alcohol intake.

Evaluation of relatives at risk: Molecular genetic testing for early diagnosis of relatives at risk to allow treatment of cardiac manifestations, diabetes mellitus, and cataracts.

Genetic counseling.

DM1 is inherited in an autosomal dominant manner. Offspring of an affected individual have a 50% chance of inheriting the expanded allele. Pathogenic alleles may expand in length during gametogenesis, resulting in the transmission of longer trinucleotide repeat alleles that may be associated with earlier onset and more severe disease than that observed in the parent. Prenatal testing and preimplantation genetic testing are possible when the diagnosis of DM1 has been confirmed by molecular genetic testing in an affected family member.

Suggestive Findings

Myotonic dystrophy type 1 (DM1) should be suspected in adults with the following:

• Muscle weakness, especially of the distal leg, hand, neck, and face
• Myotonia (sustained muscle contraction), which often manifests as the inability to quickly release a hand grip (grip myotonia) and which can be demonstrated by tapping a muscle (e.g., the thenar muscles) with a reflex hammer (percussion myotonia)
• Posterior subcapsular cataracts detectable as red and green iridescent opacities on slit lamp examination

DM1 should be suspected in neonates with some combination of the following:

• Hypotonia
• Facial muscle weakness
• Generalized weakness
• Positional malformations including clubfoot
• Respiratory insufficiency

Establishing the Diagnosis

The diagnosis of DM1 is established in a proband with identification of a heterozygous pathogenic variant in DMPK by molecular genetic testing (see Table 1).

Allele sizes. Reference ranges for allele sizes were established by the Second International Myotonic Dystrophy Consortium (IDMC) in 1999 [International Myotonic Dystrophy Consortium 2000, Moxley & Meola 2008]. See Prior [2009] and Kamsteeg et al [2012] for technical standards and guidelines for testing.

• Normal alleles. 5-34 CTG repeats
• Mutable normal (premutation) alleles. 35-49 CTG repeats. Individuals with CTG expansions in the premutation range have not been reported to have symptoms, but their children are at increased risk of inheriting a larger repeat size and thus having symptoms.
• Full-penetrance alleles. >50 CTG repeats. Full-penetrance alleles are associated with disease manifestations.

See Published Guidelines / Consensus Statements.

Molecular Genetic Testing

Testing approaches include the following:

• Targeted analysis for an increased number (i.e., an expansion) of the CTG trinucleotide repeat in DMPK
• A panel that includes testing for the DMPK CTG repeat expansion and other disorders of interest (see Differential Diagnosis) may be considered to identify the genetic cause of the condition as quickly as possible. Note: (1) Methods used in a panel may include sequence analysis, deletion/duplication analysis, and/or other non-sequencing-based tests. For this disorder a panel that includes analysis for nucleotide repeats and other non-sequencing-based tests (e.g., SMN1 copy number analysis, methylation testing for Prader-Willi syndrome, UPD14 analysis) is recommended (see Table 1). (2) Although the CTG repeat expansion will not be detected by a multigene sequencing panel, this testing may be appropriate for some conditions in the differential diagnosis. (3) The genes included in the panel and the diagnostic sensitivity of the testing used for each gene vary by laboratory and are likely to change over time. (4) Some multigene panels may include genes not associated with the condition discussed in this GeneReview. (5) In some laboratories, panel options may include a custom laboratory-designed panel and/or custom phenotype-focused exome analysis that includes genes specified by the clinician.
  For an introduction to multigene panels click here. More detailed information for clinicians ordering genetic tests can be found here.

Table 1.

Molecular Genetic Testing Used in Myotonic Dystrophy Type 1

Clinical Description

DM1 is a systemic disease potentially affecting nearly every organ system. Clinical findings in myotonic dystrophy type 1 (DM1) span a continuum from mild to severe. Udd & Krahe [2012], Thornton [2014], Turner & Hilton-Jones [2014], and Hartman et al [2024] provide an excellent overview of all aspects of DM1. The clinical findings have been categorized into three somewhat overlapping phenotypes (mild, classic, and congenital) that generally correlate with CTG repeat size (Table 2). The CTG repeat ranges for the phenotypes in Table 2 have considerable overlap and CTG repeat size should not be used to predict disease severity [Moxley & Meola 2008, Wenninger et al 2018].

Table 2.

Correlation of Phenotype and CTG Repeat Length in Myotonic Dystrophy Type 1

Genotype-Phenotype Correlations

In general, longer CTG repeat expansions correlate with an earlier age of onset and more severe disease [Logigian et al 2004] (Table 2). Small but abnormal repeats (50-99) are often associated with a mild or asymptomatic phenotype [Arsenault et al 2006].

The DMPK CTG trinucleotide repeat length is mitotically unstable in individuals with DM1. Such instability very often leads to somatic mosaicism for the size of the CTG expansion; therefore, correlation between CTG repeat size observed in one tissue and disease severity may not be possible [Moxley & Meola 2008]. Studies have attempted to estimate the progenitor allele CTG repeat length (ePAL) and somatic mutational dynamics [Cumming et al 2019]. ePAL refers to the subject's CTG repeat size at the time of birth, which often increases over the next decades. It is also known that 3%-8% of DM1 expansions contain variant repeats such as CCG and CGG. These are referred to as variant repeat interruptions and may be associated with later onset and milder phenotype [Miller et al 2020].

A person who was a compound heterozygote for expanded alleles with 1,260 and 60 CTG repeats was reported to have cerebral abnormalities [Cerghet et al 2008].

Penetrance

Penetrance is high (nearly 100% by age 50 years) when all manifestations of the disease, even those that are subtle, are sought. However, mild cases (e.g., persons with only cataracts) may be missed [Moxley & Meola 2008].

Anticipation

Because DMPK alleles of CTG length greater than 34 repeats are unstable and may expand in length during meiosis, at-risk offspring may inherit repeat lengths considerably longer than those present in the transmitting parent. This phenomenon results in anticipation, the occurrence of increasing disease severity and decreasing age of onset in successive generations.

Most often a child with early-onset, severe DM1 (i.e., congenital DM1) has inherited the expanded DMPK allele from the mother [Martorell et al 2007]. Although anticipation typically occurs in maternal transmission of the disease, anticipation with paternal transmission is possible [Moxley & Meola 2008].

In a study of children of parents with small expansions (50-100 CTG repeats), those with expanded alleles transmitted paternally had a larger increase in CTG repeats (median: 425 repeats; range: 70-2,000) than did those with maternally transmitted expanded alleles (median: 200 repeats; range: 57-1,400) [Pratte et al 2015].

Prevalence

Estimates of the prevalence of DM1 range from 1:100,000 in some areas of Japan to 1:10,000 in Iceland, with an overall estimated worldwide prevalence of 1:20,000 [Theadom et al 2014, Liao et al 2022].

A report in 2021 found a prevalence of 4.76:10,000 for DMPK CTG expansions of ≥50 CTG repeats in a newborn blood spot screening program in New York State [Johnson et al 2021]. A prevalence of 19.1:10,000 was found for premutations of 35-49 CTG repeats. These remarkably high prevalences are for DNA CTG repeat expansions and not for clinical diagnoses of myotonic dystrophy as in previous epidemiologic studies. More than half of the individuals reported by Johnson et al [2021] had CTG expansions in the 50-150 range consistent with the probability that many such individuals have few if any symptoms of myotonic dystrophy and are likely to be undiagnosed later in life. Such persons remain at risk for cardiac irregularities and may transmit an expanded CTG repeat to offspring.

Founder effects may increase the prevalence in specific regions, such as Quebec [Yotova et al 2005, Pratte et al 2015].

Evaluations Following Initial Diagnosis

To establish the extent of disease and needs in adults with classic myotonic dystrophy type 1 (DM1), the evaluations summarized in Table 3 (if not performed as part of the evaluation that led to the diagnosis) are recommended. Consensus-based care recommendations have been published both for adults [Ashizawa et al 2018] and for persons with congenital- and childhood-onset DM1 [Johnson et al 2019] and are available at www.myotonic.org.

Table 3.

Recommended Evaluations Following Initial Diagnosis in Adults with Myotonic Dystrophy Type 1

To establish the extent of disease and needs in children diagnosed with congenital DM1, the evaluations summarized in Table 4 (if not performed as part of the evaluation that led to the diagnosis) are recommended.

Table 4.

Recommended Evaluations Following Initial Diagnosis in Children with Myotonic Dystrophy Type 1

Treatment of Manifestations

Management guidelines have been developed [Turner & Hilton-Jones 2014, Ashizawa et al 2018, Johnson et al 2019].

No specific treatment exists for the progressive weakness in individuals with DM1.

A physiatrist, occupational therapist, or physical therapist can help evaluate affected individuals regarding the need for ankle-foot orthoses, wheelchairs, or other assistive devices as the disease progresses. Orthopedic surgery may benefit children with musculoskeletal deformities [Canavese & Sussman 2009].

Special education support is indicated for children with DM1.

Increased weakness in DM1 has been associated with both hypothyroidism and certain cholesterol-lowering medications (i.e., statins); thus, some strength may return if these causative factors are eliminated.

Myotonia in DM1 is typically mild to moderate and rarely requires treatment [Ricker et al 1999]. Anecdotally, some individuals have responded to mexiletine or carbamazepine. Logigian et al [2010] and Heatwole et al [2021] found mexiletine 150-200 mg 3x/day effective and safe for treating myotonia.

Pain management can be an important part of DM1 treatment. Different medications and combinations of medications work for some individuals, although none has been routinely effective; medications that have been used include mexiletine, gabapentin, nonsteroidal anti-inflammatory drugs, low-dose thyroid replacement, low-dose steroids, and tricyclic antidepressants. When used as part of a comprehensive pain management program, low-dose analgesics may provide relief.

Consultation with a cardiologist is appropriate for individuals with cardiac symptoms or EKG evidence of arrhythmia because fatal arrhythmias can occur prior to other symptoms in individuals with DM1. More advanced, invasive electrophysiologic testing of the heart may be required [Sovari et al 2007, Sochala et al 2017, Russo et al 2018].

Cataracts can be removed if they impair vision. Recurrence after surgery has been reported [Garrott et al 2004].

Males with low serum concentration of testosterone require hormone replacement therapy if they are symptomatic.

In most cases, surgical excision of pilomatrixoma including clear margins and its overlying skin is the preferred treatment [Cigliano et al 2005]. Basal cell cancers require removal.

An extensive review found no evidence for successful treatment of hypersomnia with routine psychostimulants [Annane et al 2006], although others have reported benefit [Talbot et al 2003, Wintzen et al 2007].

Prevention of Secondary Complications

Veyckemans & Scholtes [2013] have reviewed the anesthetic management of individuals with DM1. Choice of induction agents, airway care, local anesthesia, and neuromuscular blockade were found to minimize complications during surgery in individuals with DM1. Avoid using succinylcholine. Propofol-induced pain can induce myotonia. Sevoflurane has been used uneventfully.

Cardiac pacemakers or implantable cardioverter-defibrillators may prevent life-threatening arrhythmias [Wahbi et al 2012, Facenda-Lorenzo et al 2013].

Gagnon et al [2013] presented evidence that obesity, tobacco smoking, physical inactivity, and alcohol / illicit drug consumption are lifestyle risk factors associated with more severe DM1 phenotypes.

Mechanical ventilation for pulmonary insufficiency may be needed [Boussaïd et al 2018].

Gallbladder removal is sometimes required [Hilbert et al 2017].

Careful attention to anesthetic management during surgery is required [Veyckemans & Scholtes 2013, Gorelik & Flores 2018].

Surveillance

Turner & Hilton-Jones [2014] provide guidelines for surveillance.

The following are appropriate:

• Annual EKG to detect asymptomatic cardiac conduction defects. Some centers perform annual 24-hour Holter monitoring of individuals with DM1 who do not have cardiac symptoms [Sá et al 2007, Sovari et al 2007, Cudia et al 2009]. Tissue Doppler monitoring has also been proposed [Parisi et al 2007, Wahbi et al 2012].
• Annual measurement of fasting serum glucose concentration and glycosylated hemoglobin concentration, with treatment for diabetes mellitus if indicated [Matsumura et al 2009]
• Ophthalmologic examination every two years to evaluate for cataract formation
• Attention to nutritional status including mastication and trouble eating [Motlagh et al 2005, Engvall et al 2009, Umemoto et al 2009]
• Polysomnographic follow up of sleep complaints [Kumar et al 2007]

Agents/Circumstances to Avoid

Statins used to lower cholesterol may sometimes cause muscle pain and weakness.

Mathieu et al [1997] noted that "[n]umerous cases of perioperative complications in patients with DM have been reported. Hazards have been associated with the use of thiopentone, suxamethonium, neostigmine, and halothane. Most complications were pulmonary. The likelihood of perioperative pulmonary complications (PPC) was not related to any specific anesthetic drug. Because of the increased risk of PPC, careful monitoring during the early postoperative period, protection of the upper airways, chest physiotherapy, and incentive spirometry are mandatory in all symptomatic patients with DM, particularly those with a severe muscular disability or those who have undergone an upper abdominal surgery."

Veyckemans & Scholtes [2013] and Gorelik & Flores [2018] have reviewed appropriate anesthetic care for individuals with DM1 and DM2.

Malignant hyperthermia during anesthesia including the use of vecuronium [Nishi et al 2004] has been reported in DM1 but is very uncommon [Kirzinger et al 2010]. (See Malignant Hyperthermia Susceptibility.)

Aggressive doxorubicin-based chemotherapy for lymphoma in a person with DM1 produced sudden atrial fibrillations [Montella et al 2005].

Gagnon et al [2013] presented evidence that obesity, tobacco smoking, physical inactivity, and alcohol / illicit drug consumption are lifestyle risk factors associated with more severe DM1 phenotypes.

Evaluation of Relatives at Risk

It is appropriate to clarify the genetic status of apparently asymptomatic at-risk adult relatives of an affected individual to allow for early diagnosis and treatment of cardiac manifestations, diabetes mellitus, and cataracts.

See Genetic Counseling for issues related to testing of at-risk relatives for genetic counseling purposes.

Pregnancy Management

Women with DM1 are at risk for complications during pregnancy including increased spontaneous abortion rate, premature labor, prolonged labor, retained placenta, placenta previa, and postpartum hemorrhage [Zaki et al 2007, Argov & de Visser 2009]. Special surveillance during pregnancy of women with DM1 includes ultrasound examination; evaluation for placenta previa; and anticipation of possible polyhydramnios, prolonged labor, and/or need for delivery by cesarean section [Argov & de Visser 2009].

Complications related to the presence of congenital DM1 in the fetus include reduced fetal movement and polyhydramnios. Awater et al [2012] found increased rates of cesarean birth and preterm delivery among women with DM1.

See MotherToBaby for further information on medication use during pregnancy.

Therapies Under Investigation

Search ClinicalTrials.gov in the US and EU Clinical Trials Register in Europe for information on clinical studies for a wide range of diseases and conditions. Note: There may not be clinical trials for this disorder.

Other

Moderate-intensity strength training does no harm, but it is unclear whether it offers measurable benefits [van der Kooi et al 2005]. A controlled study of an exercise program for DM1 showed neither beneficial nor detrimental effects [Kierkegaard et al 2011].

Mode of Inheritance

Myotonic dystrophy type 1 (DM1) is inherited in an autosomal dominant manner.

Risk to Family Members

Parents of a proband

• Virtually all individuals with DM1 inherited their expanded CTG allele from a parent who also has an allele in the abnormal range (>34 CTG repeats); however, the parent with the expanded allele may or may not appear to be affected. The parent may appear to be unaffected because of failure to recognize symptoms of mild DM1 or the parent may have no symptoms and have an abnormal, but small, CTG repeat expansion.
• New expansions of a normal allele (≤34 CTG repeats) into the abnormal range are rare.
• If both parents of a proband are asymptomatic, it is appropriate to offer DMPK molecular genetic testing to both for the purpose of genetic counseling of other family members. In this instance, genetic counseling issues relevant to presymptomatic testing should be addressed.
• If a CTG expansion in the abnormal range (>34 repeats) cannot be detected in the leukocyte DNA of either parent, possible non-medical explanations including alternate paternity or maternity (e.g., with assisted reproduction) or undisclosed adoption could be explored.

Sibs of a proband. The risk to sibs of a proband depends on the genetic status of the parents:

• If one parent has an expanded DMPK allele, the risk to each sib is 50%.
• An expanded DMPK allele may expand further in length during gametogenesis, resulting in transmission of an allele with a larger CTG repeat that may be associated with earlier onset and more severe disease than that in the parent (see Clinical Characteristics, Anticipation; Related Genetic Counseling Issues, Empiric risks for congenital DM1).

Offspring of a proband

• Each child of an individual with an expanded DMPK allele (>34 CTG repeats) has a 50% chance of inheriting the expanded DMPK allele.
• An expanded DMPK allele may expand further in length during gametogenesis, resulting in transmission of an allele with a larger CTG repeat that may be associated with earlier onset and more severe disease than that in the parent (see Clinical Characteristics, Anticipation and Related Genetic Counseling Issues, Empiric risks for congenital DM1).

Other family members. The risk to other family members depends on the status of the proband's parent: if a parent is affected or has a CTG expansion in the abnormal range (>34 repeats), the parent's family members are at risk.

Related Genetic Counseling Issues

See Management, Evaluation of Relatives at Risk for information on evaluating at-risk relatives for the purpose of early diagnosis and treatment.

Family planning

• The optimal time for determination of genetic risk and discussion of the availability of prenatal/preimplantation genetic testing is before pregnancy.
• It is appropriate to offer genetic counseling (including discussion of potential risks to offspring and reproductive options) to young adults who are affected or at risk.

Empiric risks for congenital DM1. Data concerning the likelihood that a mother with a particular CTG repeat size will have a child with a particular CTG repeat size or phenotype may be useful in recurrence risk counseling. The available data have wide confidence limits, making specific risk estimates difficult.

• Redman et al [1993] found that for women with a CTG repeat length of 100 or higher, the risk to a child who has inherited the abnormal allele of having an expansion of 730 or more CTG repeats (and thus congenital DM1) is 62%. Martorell et al [2007] found a similar frequency of 63% of fetuses with more than 1,000 repeats in 31 of 49 maternal transmissions of the expanded allele (mothers' abnormal allele size ranging from 65 to 1,333 CTG repeats).
• Cobo et al [1995] determined that for women with a CTG repeat size smaller than 300, the risk to a child who has inherited the abnormal allele of having congenital DM1 is 10%, and for women with a CTG repeat size greater than 300, the risk to a child who has inherited the abnormal allele of having congenital DM1 is 59%. Martorell et al [2007] found a similar correlation, but there was no statistical analysis.

Diagnosis of mildly affected individuals during family evaluation. Individuals with mild DM1 are often unaware of having DM1 and may only be diagnosed in the course of evaluation of a more severely affected family member. This often occurs when an asymptomatic mother having a CTG repeat size under 100 gives birth to an infant with congenital DM1 with a CTG repeat length in the thousands.

Testing of at-risk asymptomatic adult relatives of individuals with DM1 is possible after molecular genetic testing has identified the expanded DMPK allele in an affected family member. Such testing should be performed in the context of formal genetic counseling and is not useful in predicting age of onset, severity, type of symptoms, or rate of progression in asymptomatic individuals. Testing of asymptomatic at-risk individuals with nonspecific or equivocal symptoms is predictive testing, not diagnostic testing.

Predictive testing in minors (i.e., testing of asymptomatic at-risk individuals younger than age 18 years). For asymptomatic minors at risk for adult-onset conditions for which early treatment would have no beneficial effect on disease morbidity and mortality, predictive genetic testing is considered inappropriate, primarily because it negates the autonomy of the child with no compelling benefit. Further, concern exists regarding the potential adverse effects that such information may have on family dynamics, the risk of discrimination and stigmatization in the future, and the anxiety that such information may cause.

For more information, see the National Society of Genetic Counselors position statement on genetic testing of minors for adult-onset conditions and the American Academy of Pediatrics and American College of Medical Genetics and Genomics policy statement: ethical and policy issues in genetic testing and screening of children.

Testing is appropriate to consider in symptomatic individuals in a family with an established diagnosis of DM1 regardless of age.

DNA banking. Because it is likely that testing methodology and our understanding of genes, pathogenic mechanisms, and diseases will improve in the future, consideration should be given to banking DNA from probands in whom a molecular diagnosis has not been confirmed (i.e., the causative pathogenic mechanism is unknown). For more information, see Huang et al [2022].

Prenatal Testing and Preimplantation Genetic Testing

A priori high risk. Once an expanded DMPK allele has been identified in an affected family member, prenatal testing for a pregnancy at 50% risk for DM1 and preimplantation genetic testing (PGT) are possible. No effect of trinucleotide repeat size on reproductive outcome in PGT was observed in 78 couples in which 54 females and 24 males had DM1 [Verpoest et al 2010]. In these individuals the CTG repeat size ranged from 50 to 1,330 with a mean of 410. The cumulative delivery rate was 46% in 205 cycles [Verpoest et al 2008]. In 59 cycles in 35 couples Fernández et al [2017] found a live birth per cycle rate of 18.6%. Less favorable rates were found in affected women compared to affected men.

Note: (1) Abnormal test results do not predict the age of onset or severity of the disease because of the overlap of CTG repeat length associated with the three phenotypes and the possibility of somatic mosaicism for the size of the CTG expansion. However, CTG repeat lengths of 730-1,000 or greater are more likely to be associated with congenital DM1 [Redman et al 1993, Martorell et al 2007]. (2) Ultrasound examination in the second and third trimesters may reveal decreased fetal movement and polyhydramnios, possible indicators of congenital DM1.

A priori low risk. For fetuses not known to be at increased risk for DM1, molecular genetic testing for an expanded DMPK allele may be considered if polyhydramnios and/or decreased fetal activity are observed on ultrasound examination in the third trimester.

Acknowledgments

NIH CAP Award (3 MO1 RR00425-2856)

Author History

Cameron Adams, MD; Cedars-Sinai Medical Center (1999-2004)
Thomas D Bird, MD (2004-present)

Revision History

• 14 November 2024 (tb) Revision: reference added: Maya-González et al [2024]
• 21 March 2024 (tb) Revision: references added: Heatwole et al [2021], Liao et al [2022], Hartman et al [2024], Patel et al [2024]
• 25 March 2021 (tb) Revision: addition to Prevalence; reference added: Johnson et al [2021]
• 29 October 2020 (tb) Revision: addition to Genotype-Phenotype Correlations; reference added: Miller et al 2020
• 3 October 2019 (tb) Revision: additions to Genotype-Phenotype Correlations and Management; references added: Cumming et al 2019, Johnson et al 2019
• 6 December 2018 (ma) Revision: updated practice guidelines
• 12 July 2018 (sw) Comprehensive update posted live
• 10 September 2015 (me) Comprehensive update posted live
• 16 May 2013 (me) Comprehensive update posted live
• 8 February 2011 (me) Comprehensive update posted live
• 15 November 2007 (me) Comprehensive update posted live
• 17 September 1999 (me) Review posted live
• 31 December 1998 (ca) Original submission

Published Guidelines / Consensus Statements

• Ashizawa T, Gagnon C, Groh WJ, Gutmann L, Johnson NE, Meola G, Moxley R 3rd, Pandya S, Rogers MT, Simpson E, Angeard N, Bassez G, Berggren KN, Bhakta D, Bozzali M, Broderick A, Byrne JLB, Campbell C, Cup E, Day JW, De Mattia E, Duboc D, Duong T, Eichinger K, Ekstrom AB, van Engelen B, Esparis B, Eymard B, Ferschl M, Gadalla SM, Gallais B, Goodglick T, Heatwole C, Hilbert J, Holland V, Kierkegaard M, Koopman WJ, Lane K, Maas D, Mankodi A, Mathews KD, Monckton DG, Moser D, Nazarian S, Nguyen L, Nopoulos P, Petty R, Phetteplace J, Puymirat J, Raman S, Richer L, Roma E, Sampson J, Sansone V, Schoser B, Sterling L, Statland J, Subramony SH, Tian C, Trujillo C, Tomaselli G, Turner C, Venance S, Verma A, White M, Winblad S. Consensus-based care recommendations for adults with myotonic dystrophy type 1. Neurol Clin Pract. 2018;8:507-20. [PubMed]
• Committee on Bioethics, Committee on Genetics, and American College of Medical Genetics and Genomics Social, Ethical, Legal Issues Committee. Ethical and policy issues in genetic testing and screening of children. Available online. 2013. Accessed 6-6-23.
• Kamsteeg EJ, Kress W, Catalli C, Hertz JM, Witsch-Baumgartner M, Buckley MF, van Engelen BG, Schwartz M, Scheffer H. Best practice guidelines and recommendations on the molecular diagnosis of myotonic dystrophy types 1 and 2. Eur J Hum Genet. 2012;20:1203-8. [PubMed]
• National Society of Genetic Counselors. Position statement on genetic testing of minors for adult-onset conditions. Available online. 2018. Accessed 6-6-23.
• Prior TW. American College of Medical Genetics (ACMG) Laboratory Quality Assurance Committee technical standards and guidelines for myotonic dystrophy type 1 testing. Available online. 2009. Accessed 6-6-23.

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