Diagnosis Of Myotonic Dystrophy Type Research Articles

Maternal cell contamination in postnatal umbilical cord blood samples implies a low risk for genetic misdiagnoses.

Maternal cell contamination (MCC) poses a risk for misdiagnosis in prenatal genetic testing, and is examined in accredited diagnostic laboratories However, the awareness of possible MCC in perinatal/postnatal genetic testing, mainly of umbilical cord blood (CB), is lower. We investigated the rate of MCC in DNA from both umbilical CB samples and umbilical cord samples that were sent to our diagnostic laboratory for diagnostic testing between 1995 and 2021 (n=236). MCC was detected in 4% of umbilical CB samples, and in one umbilical cord sample. Particularly tests enriching for a specific variant are very sensitive for low amounts of MCC, as we emphasize here with a false positive diagnosis of myotonic dystrophy type 1 in a newborn. Overall, with appropriate collection and use, umbilical CB and umbilical cord samples are suitable for genetic testing based on the low rates of MCC and misdiagnosis. These findings do however underline the importance of routine MCC testing in umbilical CB samples and umbilical cord samples for both requesting clinicians and diagnostic genetic laboratories.

Progeroid dermatological manifestations in myotonic dystrophy type 1. Case report

Introduction: myotonic dystrophy type 1 is an autosomal dominant genetic disease with highly variable expressivity. Among the systemic alterations that are part of the clinical manifestations are neurodegeneration and premature aging, which is why it is part of progeroid syndromes. Objective: to describe progeroid dermatological manifestations in type 1 myotonic dystrophy. Case report: 44-year-old patient who, at the age of 9, confirmed a clinical diagnosis of myotonic dystrophy type 1. A family history with the same genetic disorder was collected. It presents dysmorphic signs in the skull, face, extremities and in different organs, among which are bilateral sensorineural deafness, early-onset cataracts, as well as dermatological manifestations such as seborrheic dermatitis and other lesions reminiscent of ichthyosis. Conclusions: DM1 is often referred to as a progeroid syndrome, which implies assuming that it exposes the usual underlying mechanisms of aging that are also those that participate in the pathogenesis of DM1 and in turn justify the dermatological manifestations observed

1008 Excessive daytime sleepiness in myotonic dystrophy treated with modafinil

Abstract Introduction Physiology of excessive daytime sleepiness (EDS) in myotonic dystrophy type 1 (DM1) remains incompletely understood and best practice treatment approaches are unclear. Report of case(s) We present a 73-year-old man with atrial fibrillation, implantable cardioverter defibrillator for inducible ventricular tachycardia, hypertension, and severe obstructive sleep apnea (OSA) was referred after a recent diagnosis of myotonic dystrophy type 1 (DM1) for EDS. He presented with foot pain, balance issues, and falls. A subdural hemorrhage from a fall prompted thorough evaluation including electromyography. This showed length-dependent polyneuropathy type pattern with features of subacute and chronic denervation change and myotonic discharges in right vastus medialis and bilateral tibialis anterior and gastrocnemius muscles. Myotonic Syndrome Advanced Evaluation revealed with a repeat expansion mutation in DMPK gene (85 and 13 CTG repeats). He was previously diagnosed severe OSA with an AHI of 64 and titrated onto bilevel. He recalled no improvement in symptoms with bilevel. He noted sleeping 10-12 hours per night and feeling rested. However, he takes multiple times per day for hours at a time. When actively working on tasks he feels alert and focused. Epworth sleepiness scale (ESS) was 12. Polysomnogram on bilevel followed by MSLT demonstrated control of OSA and mean sleep onset latency of 8 minutes and 5 sleep onset REM periods. With relatively little impairment and a desire for intermittent improved wakefulness, he was started on modafinil 200mg daily as needed. He reported a robust response to modafinil without the need for additional naps or cardiac complications thus far. Repeat ESS only improved to 10. Conclusion This case highlights the need for a precision medicine approach as subpopulations exist even within the specific diagnosis excessive daytime sleepiness in myotonic dystrophy. People with DM1 have been similarly reported with little improvement in ESS but dramatic subjective improvement in symptoms with modafinil. A Cochrane Review and a European Medicines Agency recommendations on modafinil are not supportive of its use in DM1 despite a subpopulation with a clear response. Interestingly, clinical measures do not seem to predict response to modafinil, suggesting unmeasured and, potentially, varied pathologies of excessive daytime sleepiness in DM1. Support (if any)

Neurogenetics: Congenital Myotonic Dystrophy with asymptomatic mother may be missed by whole exome sequencing; Biopsy, DMPK1 gene testing and EMG may be required to resolve VUS in neonates, A Case report. (P6-8.010)

<h3>Objective:</h3> We show how biopsy, EMG, and <i>DMPK1</i> gene testing may be required for variant resolution. Whole exome sequencing revealed <i>NEB</i> (nebulin) (OMIM #161650) variants of uncertain significance inherited in <i>trans</i>. Muscle biopsy and EMG were helpful in resolving <i>NEB</i> VUS (variants of uncertain significance) and the detection of myotonia even as young as 6 days of age, with a clinically asymptomatic mother. <h3>Background:</h3> Myotonic dystrophy type 1 (myotonia dystrophia 1) is an autosomal dominant multisystem disorder caused by CTG expansion of the <i>DMPK1</i> gene (dystrophia myotonica protein kinase) (OMIM #605377) resulting in anticipation, whereby offspring have greater repeat expansion and severity. <h3>Design/Methods:</h3> <h3>Case Report:</h3> This full-term patient was born with severe hypotonia and respiratory depression. Brain MRI, EEG, Karyotype (46, XY) and FISH were normal. Whole Exome Sequencing (WES) revealed heterozygous <i>NEB</i> VUS, in <i>trans</i>, but histochemical and electron microscopic examinations of the muscle biopsy did not show nemaline rods. EMG was performed and revealed myotonic discharges. A genetic diagnosis of myotonic dystrophy type 1 was made, with over 200 CTG repeats in the <i>DMPK1</i> gene. A week after tracheostomy and g-tube placement, oxcarbazepine was trialed, after which he was able to be weaned off ventilation and discharged to home. He made substantial progress over the next year. <h3>Results:</h3> NA <h3>Conclusions:</h3> Neonatal muscle biopsies may not show nemaline rods due to being early or sampling error and thus further testing may be required. When evaluating severe congenital myopathies, testing for myotonic dystrophy should be considered. Myotonia may be found in neonates as young as 6 days old characterized as briefer duration with waning repetitive small amplitudes between 50–100uV without the classic sound on a spectrum with complex repetitive discharges. Severe congenital myotonic dystrophy patients may be born from an asymptomatic mother and the diagnosis may be missed by whole exome sequencing. <b>Disclosure:</b> Mr. Appiah has nothing to disclose. Dr. Shergelashvili has nothing to disclose. Dr. Marr has nothing to disclose. Ahmed Eldokla has nothing to disclose. Dr. LEBEL has nothing to disclose. Dr. Sakonju has nothing to disclose.

Clinical score for early diagnosis of myotonic dystrophy type 2

IntroductionMyotonic dystrophy type 2 (DM2) is a rare, multisystemic, autosomal dominant disease with highly variable clinical presentation. DM2 is considered to be highly underdiagnosed.ObjectiveThe aim of this study was to determine which symptoms, signs, and diagnostic findings in patients referred to neurological outpatient units are the most indicative to arouse suspicion of DM2. We tried to make a useful and easy-to-administer clinical scoring system for early diagnosis of DM2-DM2 early diagnosis score (DM2-EDS).Patients and methodsTwo hundred ninety-one patients with a clinical suspicion of DM2 were included: 69 were genetically confirmed to have DM2, and 222 patients were DM2 negative. Relevant history, neurological, and paraclinical data were obtained from the electronic medical records.ResultsThe following parameters appeared as significant predictors of DM2 diagnosis: cataracts (beta = 0.410, p < 0.001), myotonia on needle EMG (beta = 0.298, p < 0.001), hand tremor (beta = 0.211, p = 0.001), positive family history (beta = 0.171, p = 0.012), and calf hypertrophy (beta = 0.120, p = 0.043). In the final DM2-EDS, based on the beta values, symptoms were associated with the following values: cataracts (present 3.4, absent 0), myotonia (present 2.5, absent 0), tremor (present 1.7, absent 0), family history (positive 1.4, negative 0), and calf hypertrophy (present 1.0, absent 0). A cut-off value on DM2-EDS of 3.25 of maximum 10 points had a sensitivity of 84% and specificity of 81% to diagnose DM2.ConclusionSignificant predictors of DM2 diagnosis in the neurology outpatient unit were identified. We made an easy-to-administer DM2-EDS score for early diagnosis of DM2.

Unexpected diagnosis of myotonic dystrophy type 2 repeat expansion by genome sequencing

Several neurological disorders, such as myotonic dystrophy are caused by expansions of short tandem repeats (STRs) which can be difficult to detect by molecular tools. Methodological advances have made repeat expansion (RE) detection with whole genome sequencing (WGS) feasible. We recruited a multi-generational family (family A) ascertained for genetic studies of autism spectrum disorder. WGS was performed on seven children from four nuclear families from family A and analyzed for REs of STRs known to cause neurological disorders. We detected an expansion of a heterozygous intronic CCTG STR in CNBP in two siblings. This STR causes myotonic dystrophy type 2 (DM2). The expansion did not segregate with the ASD phenotype. Repeat-primed PCR showed that the DM2 CCTG motif was expanded above the pathogenic threshold in both children and their mother. On subsequent examination, the mother had mild features of DM2. We show that screening of STRs in WGS datasets has diagnostic utility, both in the clinical and research domain, with potential management and genetic counseling implications.

A patient with myotonic dystrophy diagnosed after experiencing sudden respiratory failure: a case report

BackgroundMyotonic dystrophy is a disorder affecting multiple organs including skeletal muscles and causes respiratory failure. We describe a patient who developed respiratory failure, with delayed diagnosis of myotonic dystrophy type 1 as the cause.Case presentationA 62-year-old woman developed acute onset of dyspnea after showing hypertension and tachycardia and was transported to our hospital. On arrival at our institution, SpO2 was 80% with a non-rebreather mask. With a diagnosis of acute phase heart failure, she underwent tracheal intubation. However, weaning from the respirator was difficult in the intensive care unit (ICU). A detailed interview revealed that her brother was affected with myotonic dystrophy type 1. She was also diagnosed with myotonic dystrophy type 1 by a genetic test.ConclusionsTaking a careful past and family history and prompt genetic testing is required on suspicion of neuromuscular diseases in a patient with respiratory failure by an unknown cause.

Cognitive behavioural therapy with optional graded exercise therapy in patients with severe fatigue with myotonic dystrophy type 1: a multicentre, single-blind, randomised trial

Myotonic dystrophy type 1 is the most common form of muscular dystrophy in adults and leads to severe fatigue, substantial physical functional impairment, and restricted social participation. In this study, we aimed to determine whether cognitive behavioural therapy optionally combined with graded exercise compared with standard care alone improved the health status of patients with myotonic dystrophy type 1. We did a multicentre, single-blind, randomised trial, at four neuromuscular referral centres with experience in treating patients with myotonic dystrophy type 1 located in Paris (France), Munich (Germany), Nijmegen (Netherlands), and Newcastle (UK). Eligible participants were patients aged 18 years and older with a confirmed genetic diagnosis of myotonic dystrophy type 1, who were severely fatigued (ie, a score of ≥35 on the checklist-individual strength, subscale fatigue). We randomly assigned participants (1:1) to either cognitive behavioural therapy plus standard care and optional graded exercise or standard care alone. Randomisation was done via a central web-based system, stratified by study site. Cognitive behavioural therapy focused on addressing reduced patient initiative, increasing physical activity, optimising social interaction, regulating sleep-wake patterns, coping with pain, and addressing beliefs about fatigue and myotonic dystrophy type 1. Cognitive behavioural therapy was delivered over a 10-month period in 10-14 sessions. A graded exercise module could be added to cognitive behavioural therapy in Nijmegen and Newcastle. The primary outcome was the 10-month change from baseline in scores on the DM1-Activ-c scale, a measure of capacity for activity and social participation (score range 0-100). Statistical analysis of the primary outcome included all participants for whom data were available, using mixed-effects linear regression models with baseline scores as a covariate. Safety data were presented as descriptives. This trial is registered with ClinicalTrials.gov, number NCT02118779. Between April 2, 2014, and May 29, 2015, we randomly assigned 255 patients to treatment: 128 to cognitive behavioural therapy plus standard care and 127 to standard care alone. 33 (26%) of 128 assigned to cognitive behavioural therapy also received the graded exercise module. Follow-up continued until Oct 17, 2016. The DM1-Activ-c score increased from a mean (SD) of 61·22 (17·35) points at baseline to 63·92 (17·41) at month 10 in the cognitive behavioural therapy group (adjusted mean difference 1·53, 95% CI -0·14 to 3·20), and decreased from 63·00 (17·35) to 60·79 (18·49) in the standard care group (-2·02, -4·02 to -0·01), with a mean difference between groups of 3·27 points (95% CI 0·93 to 5·62, p=0·007). 244 adverse events occurred in 65 (51%) patients in the cognitive behavioural therapy group and 155 in 63 (50%) patients in the standard care alone group, the most common of which were falls (155 events in 40 [31%] patients in the cognitive behavioural therapy group and 71 in 33 [26%] patients in the standard care alone group). 24 serious adverse events were recorded in 19 (15%) patients in the cognitive behavioural therapy group and 23 in 15 (12%) patients in the standard care alone group, the most common of which were gastrointestinal and cardiac. Cognitive behavioural therapy increased the capacity for activity and social participation in patients with myotonic dystrophy type 1 at 10 months. With no curative treatment and few symptomatic treatments, cognitive behavioural therapy could be considered for use in severely fatigued patients with myotonic dystrophy type 1. The European Union Seventh Framework Programme.

Successful treatment of a patient with statin-induced myopathy and myotonic dystrophy type II with proprotein convertase subtilisin/kexin type 9 inhibitor, alirocumab (Praluent)

Presently there are limited treatment options for hypercholesterolemia in patients with statin intolerance and myotonic dystrophy. A 74 year-old male presented to endocrine clinic with hypercholesterolemia (serum LDL-C 210 mg/dL), hypogonadism, insulin-controlled type 2 diabetes mellitus, and minimally elevated serum creatine kinase (CK) levels (184 U/L, ref. range 38-174). Shortly after simvastatin treatment, patient developed severe myalgias in the proximal lower and upper extremities; and serum CK increased to 317 U/L. Subsequently patient was treated with various statins including rosuvastatin with similar outcomes. Patient was also treated with bile acid binding resin and ezetimibe without improvement. At this time, a diagnosis of myotonic dystrophy type 2 was confirmed. Patient was then treated with alirocumab, a PCSK9 inhibitor 75 mg subcutaneously every 2 weeks with significant improvement in LDL-C (90 mg/dL) and myalgias. In conclusion, PCSK9 inhibitors such as alirocumab may be an excellent lipid lowering agent in patients with statin intolerance and myotonic dystrophy.

Biomolecular diagnosis of myotonic dystrophy type 2: a challenging approach.

Myotonic dystrophy type 1 (DM1) and type 2 (DM2) are the most common adult form of muscular dystrophy, characterized by autosomal dominant progressive myopathy, myotonia, and multiorgan involvement. The onset and symptoms of the myotonic dystrophies are diverse, complicating their diagnoses and limiting a comprehensive approach to their clinical care. Diagnostic delay in DM2 is due not only to the heterogeneous phenotype and the aspecific onset but also to the unfamiliarity with the disorder by most clinicians. Moreover, the DM2 diagnostic odyssey is complicated by the difficulties to develop an accurate, robust, and cost-effective method for a routine molecular assay. The aim of this review is to underline by challenging approach the diagnostic limits and pitfalls that could results in failure to recognize the presence of DM2 disease. Understanding and preventing delays in DM2 diagnosis may facilitate family planning, improve symptom management in the short term, and facilitate more specific treatment in the long term.

Analysis of CTG repeat length variation in the DMPK gene in the general population and the molecular diagnosis of myotonic dystrophy type 1 in Malaysia

ObjectiveThe lack of epidemiological data and molecular diagnostic services in Malaysia has hampered the setting-up of a comprehensive management plan for patients with myotonic dystrophy type 1 (DM1), leading to...

Application of a reliable and rapid polymerase chain reaction based method in the diagnosis of myotonic dystrophy type 1 (DM1) in India

DM1 is caused by CTG repeat expansion in the 3′-UTR of the DMPK gene. DM1 patients have expansions of greater than 50 repeats and up to many thousands. The intention of the present study is the establishment of reliable and rapid polymerase chain reaction methodology in early screening of DM1 patients and their family members. PCR followed by TP-PCR was assessed for screening of 27 cases (from 26 families) and 75 family members and 300 control samples. All patients had CTG repeat expansion while forty seven (63%) and twenty eight (37%), out of seventy five family members were heterozygous and homozygous respectively. Similarly, two hundred thirty (76.77%) and seventy (23.33%), out of three hundred control subjects were heterozygous and homozygous respectively and the number of repeats varied from 5 to 35. Thirteen complete family screenings were done. Thus, TP-PCR is a reliable and rapid molecular technique for the detection of CTG repeat expansion in DM1.

WASTED AND WEAK ARM IN A YOUNG MAN

IntroductionThere are many causes of progressive muscle wasting and weakness from which motor neuron disease (MND) is a common and dreaded differential diagnosis. Routine investigations such as neurophysiology study, imaging...

Value of short exercise and short exercise with cooling tests in the diagnosis of myotonic dystrophies (DM1 AND DM2)

Standard electromyography (EMG) is useful in the diagnosis of myotonic dystrophy type 1 (DM1) and type 2 (DM2), but it does not differentiate between them. The aim of this study was to estimate the utility of the short exercise test (SET) and short exercise test with cooling (SETC) in differentiating between DM1 and DM2. SET and SETC were performed in 32 patients with DM1 (mean age 35.8 ± 12.7 years) and 28 patients with DM2 (mean age 44.5 ± 12.5 years). We observed a significant decline in compound motor action potential (CMAP) amplitude in DM1 with both SET and SETC immediately after effort. In DM2, there was no marked change in CMAP amplitude with either SET or SETC. SET and SETC may serve as useful tools for clinical differentiation between DM1 and DM2, and they may be used as a guide for molecular testing.

Mechanical and Electrophysiological Substrate for Recurrent Atrial Flutter Detected by Right Atrial Speckle Tracking Echocardiography and Electroanatomic Mapping in Myotonic Dystrophy Type 1

A 48-year-old patient with myotonic dystrophy (MD) type 1, recurrent typical atrial flutter (AF), and otherwise unremarkable history was hospitalized for an electrophysiological study. The diagnosis of MD type 1 had been made 25 years earlier and was based on typical clinical features and confirmation by genetic analysis. The ECG pattern of AF was characterized by negative waves in the inferior leads and positive waves in V1, a cycle length of 280 milliseconds, and 2:1 atrioventricular conduction. At the time of the study, the patient was asymptomatic and showed normal findings at the cardiac physical examination, ECG, and standard echocardiography. Preablation ECG showed sinus rhythm at 60 bpm with a normal PR interval (180 milliseconds), regular QRS duration and morphology, and normal ventricular repolarization. Average septal-lateral mitral annulus velocities (s′, 9.5 cm/s; e′, 10.3 cm/s; a′, 7.4 cm/s), the E/e′ ratio (7.3), and left ventricular global longitudinal and circumferential strain (−21.5% and −23.2%, respectively) were all normal, as well as right ventricular systolic function (tricuspid annulus systolic excursion and peak systolic velocity, 25 mm and 18.5 cm/s, respectively). Analysis of longitudinal right atrial deformation by speckle tracking showed impaired strain mechanics in the inferior segment of the atrial …

Validation of Sensitivity and Specificity of Tetraplet-Primed PCR (TP-PCR) in the Molecular Diagnosis of Myotonic Dystrophy Type 2 (DM2)

Myotonic dystrophy type 2 (DM2, OMIM #602688) is a multisystemic hereditary degenerative disease caused by a tetranucleotide CCTG expansion in the ZNF9 gene. Routine testing strategies for DM2 require the use of Southern blot or long-range PCR, but the presence of very large expansions and wide somatic mosaicism greatly reduce the sensitivity of these reference techniques. We therefore developed and validated a tetraplet-primed PCR (TP-PCR) method to detect the DM2 mutation by testing 87 DM2-positive and 76 DM2-negative previously characterized patients. The specificity of this technique was evaluated including DNA samples from 39 DM1-positive patients. We then attempted a prospective analysis of 50 patients with unknown genotype who referred to our center for diagnostic or presymptomatic tests. Results show that TP-PCR is a fast, reliable, and flexible technique, whose specificity and sensitivity is almost 100%, with no false positive or negative results either in retrospective and prospective applications. We therefore conclude that using this technique, in combination with the short-range PCR, is sufficient to correctly establish the presence or the absence of ZNF9 expanded alleles in the molecular diagnosis of DM2.

Distribution of CTG repeats at the DMPK gene in myotonic distrophy patients and healthy individuals from the Mexican population

Myotonic dystrophy type 1 (DM1), the most common form of adult muscular dystrophy, is caused by anormal expansion of CTG trinucleotide repeats located in the 3'-untranslated region of the DMPK gene. The clinical features of DM1 are multisystemic and highly variable, and the unstable nature of CTG expansion causes wide genotypic and phenotypic presentations. In this study, we described to our knowledge for the first time the molecular diagnosis of myotonic dystrophy type 1 patients in the Mexican population, applying a fluorescent PCR method in combination with capillary electrophoresis analysis of the amplified products. We identified expanded alleles in 45 out of 50 patients (90%) with clinical features of myotonic disease. Furthermore, genotyping of 400 healthy subjects revealed the presence of 25 different alleles, ranging in size from 5 to 34 repeats. The most frequent allele was 13 CTG repeats (38.87%) and the frequency for alleles over 18 CTG repeats was 6.7%. Molecular test is essential for DM1 diagnosis and distribution of the CTG repeat alleles present in the Mexican population are significantly different from those of other populations.

The use of buccal cells for rapid diagnosis of myotonic dystrophy type 1

AbstractType 1 myotonic dystrophy (DM1) is an autosomal dominant disorder caused by a CTG repeat expansion. RNA containing expanded CUG repeats does not leave the nucleus, but accumulates in discrete nuclear foci which sequester the human muscleblind-like (MBNL) proteins. We have examined buccal cells from 15 adult DM1 patients and 7 control non-DM patients to determine whether nuclear foci can be detected by either immunostaining for MBNL1 protein or fluorescent in situ hybridisation (FISH) for the CUG repeat RNA. Both methods detected nuclear foci in all three early-onset patients, but only in a minority of 12 less severe DM1 patients. There were no false-positive results in the 7 controls. Although the method does not reliably identify all DM1 patients, it may prove useful as a rapid test for severe congenital DM1 in floppy babies.

Use of RNA Fluorescence In Situ Hybridization in the Prenatal Molecular Diagnosis of Myotonic Dystrophy Type I

Myotonic dystrophy type 1 (DM1; OMIM #160900) is an autosomal-dominant genetic disorder with multisystemic clinical features associated with a CTG expansion in the 3' untranslated region of the DMPK gene on chromosome 19q13.3. A long-PCR protocol to detect the DM1 expansion is rapid, sensitive, and accurate, but interpretative limitations can occur when the expansion size exceeds the PCR amplification range and in cases of somatic mosaicism. To overcome these problems, we used RNA fluorescence in situ hybridization (RNA-FISH) to study cultured cells derived from chorionic villus samples (CVS) with the DM1 mutation. The RNA-FISH method is designed to detect the distinctive DM1 cellular phenotype, characterized by the presence of nuclei with focal ribonuclear inclusions (foci) containing the DMPK expanded transcripts. We analyzed 6 CVS from DM1-predicted pregnancies and 6 CVS from DM1-negative pregnancies. In 4 DM1-predicted fetuses with a CTG expansion >200 CTG, varying numbers of ribonuclear inclusions were clearly visible in all cells. One case with a somatic mosaicism for the DMPK mutation showed 15% of cells with no nuclear foci. No nuclear signals were detected in all controls examined (n = 6) and in 1 DM1-positive sample with a CTG expansion <100 copies. Nuclear foci, and therefore the DM1 mutation they are caused by, can be detected efficiently on interphase nuclei of trophoblast cells with RNA-FISH when the CTG expansion is >200 copies.

New methods for molecular diagnosis and demonstration of the (CCTG) n mutation in myotonic dystrophy type 2 (DM2)

Myotonic dystrophy types 1 and 2 are autosomal dominant, multisystemic disorders with many similarities in their clinical manifestations. Myotonic dystrophy type 1 is caused by a (CTG) n expansion in the 3′ untranslated region of the DMPK gene in 19q13.3 and myotonic dystrophy type 2 by a (CCTG) n expansion in intron 1 of ZNF9 in 3q21.3. However, the clinical diagnosis of myotonic dystrophy type 2 is more complex than that of myotonic dystrophy type 1, and conventional molecular genetic methods used for diagnosing myotonic dystrophy type 1 are insufficient for myotonic dystrophy type 2. Herein we describe two in situ hybridization protocols for the myotonic dystrophy type 2 mutation detection. Chromogenic in situ hybridization was used to detect both the genomic expansion and the mutant transcripts in muscle biopsy sections. Chromogenic in situ hybridization can be used in routine myotonic dystrophy type 2 diagnostics. Fluorescence in situ hybridization on extended DNA fibers was used to directly visualize the myotonic dystrophy type 2 mutation and to estimate the repeat expansion sizes.