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Myotonic Dystrophy


Myotonic dystrophy is a kind of multisystem disease, which is inherited in nature. It is a chronic disease condition that gradually progresses, causing muscle wasting, myotonia, heart defects and development of cataracts.


Myotonic dystrophy significantly affects multiple organs and systems involving the skeletal system, cardiac muscles and smooth muscles of the heart. Signs and symptoms of myotonic dystrophy vary with the type of condition that has set in. Some of the common symptoms experienced by the individuals include development of myotonia, characterized by difficulty in releasing grip, abnormal rhythm of heart, weakening of the muscles of upper and lower limbs [6].

Affected individuals also complain of difficulty in swallowing. In addition to these symptoms, individuals also experience cognitive impairment, sleeping difficulties, sleepiness during daytime, development of cataract in early years and infertility [7].

  • In this cohort (186 females, 121 males), a proximal weakness was the leading symptom at onset (55.4%), followed by myalgia (35.5%) and myotonia (25.4%).[ncbi.nlm.nih.gov]
  • Primary role is that of neurologist who treats the muscle weakness with help of drug known as mexiletine.[symptoma.com]
  • The muscle weakness associated with type 1 particularly affects the lower legs, hands, neck, and face. Muscle weakness in type 2 primarily involves the muscles of the neck, shoulders, elbows, and hips.[web.archive.org]
  • This study aims to investigate the use of a scale previously described for the assessment and rating of ataxia (SARA) with the hypothesis that it could have utility in DM1 patients as a measure of disease severity and risk of falling.[ncbi.nlm.nih.gov]
  • Remove loose carpeting from the floor to reduce your risk for a fall. Use chairs with side arms and hard cushions to make it easier to get up or out of a chair. Put grab bars on the walls beside toilets and inside showers and bathtubs.[drugs.com]
  • Individuals with family history of disorder are at an increased risk of falling prey to it.[symptoma.com]
  • One of the main dangers with the disease is that people cannot have general anesthetics, so falling seriously ill can carry added problems.[metro.co.uk]
  • In the later stages of the disease, some people experience sleep apnea and hypersomnia. Women with myotonic dystrophy have an increased risk for pregnancy complications.[en.wikibooks.org]
  • Psychostimulants for hypersomnia (excessive daytime sleepiness) in myotonic dystrophy. Cochrane Database Syst Rev. 2006; 3 :CD003218. [ PubMed : 16855999 ] Antonini G, Soscia F, Giubilei F, De Carolis A, Gragnani F, Morino S, Ruberto A, Tatarelli R.[web.archive.org]
  • Apathy and hypersomnia are common features of myotonic dystrophy.[ncbi.nlm.nih.gov]
  • ., organization, concentration, word-finding) and hypersomnia. Conduction abnormalities are more common in DM1 than DM2, but all people are advised to have an annual ECG. Both types are also associated with insulin resistance.[en.wikipedia.org]
Male Hypogonadism
  • Phenotype includes myotonia, limb muscle weakness, muscle atrophy, facial weakness, ptosis, and multi-organ involvement including cataracts, insulin resistance, elevated liver enzyme levels, male hypogonadism and cardiac conduction defects [ 1 ].[bmcresnotes.biomedcentral.com]
Mitral Valve Prolapse
  • Mitral valve prolapse in 20%. First-degree AV block is common. MD2 also leads to myotonia and muscle dysfunction, but cardiac conduction defects are less common.[openanesthesia.org]
  • BACKGROUND: The most frequent skin features associated with myotonic dystrophy type 1 (DM1) are frontal alopecia and pilomatrixomas. Several reports suggest that the incidence of basal cell carcinoma is increased in DM1.[ncbi.nlm.nih.gov]
  • Other typical findings of the disease were frontal alopecia, bilateral palpebral ptosis, testicular atrophy, muscular weakness with distal predominance, generalized hyporeflexia, and moderate mental retardation.[revespcardiol.org]
  • Pressure - Low pressure Possibly due to ciliary body detachment SLE: L/L: Blepharoptosis. Brow ptosis.[eyewiki.aao.org]
  • Distal myopathy with rimmed vacuoles is allelic to hereditary inclusion body myopathy. Neurology. 2002; 59 :1689–93. [ PubMed : 12473753 ] Pellizzoni L, Lotti F, Maras B, Pierandrei-Amaldi P.[ncbi.nlm.nih.gov]
  • Sottoclasse di myotonic disease, cardiomiopatia ipertrofica, sindrome cerebrale organica, blefaroptosi, myopathy with eye involvement, syndrome associated with hypertrophic cardiomyopathy, musculoskeletal disease with cataract, Hypergonadotropic hypogonadism[commons.wikimedia.org]
Muscular Atrophy
  • He published numerous works on subjects such as aphthongia (1902) and cerebral muscular atrophy (1903). [3], [4] In December 1904, he filed for habilitation with his thesis: “New contributions on the theory of muscular atrophy in supranuclear paralyses[doi.org]
  • Patreon Help with Search Health Conditions and Diseases Neurological Disorders Muscle Diseases Myotonic Dystrophy 0 An autosomal dominant neuromuscular disorder which usually presents in early adulthood, characterized by progressive muscular atrophy ([curlie.org]
  • Neuromuscular disorders like myotonic dystrophy (dystrophia myotonica or Steinert's disease) and spinal muscular atrophy are associated with perioperative complications related to muscle weakness.[ncbi.nlm.nih.gov]
Muscle Cramp
  • Pregnancy is an aggravating factor for pain, myotonia and muscle cramps. Affected subjects often complain of sweaty palms.[dystrophiemyotonique.chuq.qc.ca]
  • For example, a child with the condition may: learn to walk later than usual have muscle cramps when exercising struggle with sports at school During late childhood or early adulthood, people with Becker MD often find they have difficulty running, walking[nhs.uk]
Limb Weakness
  • Patient-reported perceived changes (worse/stable) in balance, walking, lower-limb weakness, stair-climbing and hand weakness were used as criteria.[ncbi.nlm.nih.gov]
  • The disease had been previously unknown to the family and the patient had no typical DM1 symptoms like limb weakness or myotonia.[bmcresnotes.biomedcentral.com]
  • Neck braces can also be prescribed for neck muscle weakness. [9] Mobility aids and adaptive equipment [ edit ] Upper and lower limb weakness, visual impairments and myotonia may lead to the need for mobility aids and functional adaptive equipment such[en.wikipedia.org]
  • Symptoms of oculopharyngeal MD can include: droopy eyelids difficulty swallowing (dysphagia) progressive restriction of eye movement as the eye muscles become affected limb weakness around the shoulders and hips As the eyelids droop, they can cover the[nhs.uk]
Speech Disability
  • Both myotonia and weakness are observed in patients with swallowing and speech disability. Myotonia, delayed muscular relaxation following contraction, is most frequently apparent in the tongue, forearm, and hand.[flybase.org]
  • Myotonic dystrophy initially manifested by speech disability. J Speech Hear Disord 1968 ; 33 : 51 –9. Darley FL, Aronson AE, Brown JR. Motor speech disorders. Philadelphia: WB Saunders Co, 1975. McNeil MR.[jnnp.bmj.com]
  • Other typical findings of the disease were frontal alopecia, bilateral palpebral ptosis, testicular atrophy, muscular weakness with distal predominance, generalized hyporeflexia, and moderate mental retardation.[revespcardiol.org]
  • Sleep apnea contributes to the daytime somnolence but patients often continue to have daytime sleepiness after CPAP.[myotonic.org]
  • Curschmann 4 described his patients as exhibiting moodiness, suspiciousness, and dullness. 4 Later, Rohrer 17 and Naegeli 18 made the same observations and depicted their subjects as mellow, somnolent, and disagreeable.[jamanetwork.com]
Nasal Speech
  • speech, no distal weakness except isolated digitis flexor weakness); Grade 3 - distal weakness (no proximal weakness, except isolated triceps brachii weakness); Grade 4 - mild or moderate proximal weakness; Grade 5 - severe proximal weakness (confined[scielo.br]


Diagnosis of myotonic dystrophy involves various laboratory studies followed by taking note of family history of the disease and physical examination. The laboratory tests include electrodiagnostic testing, blood tests and muscle biopsy. Of these, muscle biopsy tests hold primary importance to evaluate the reason behind development of muscle weakness. Blood tests would help in identifying the specific gene that is causing the disorder. Various tests to determine heart and lung functioning would also be carried out.

In addition to all the above methods, predictive testing will also be done which can help in identifying the risks of developing myotonic dystrophy much before the signs and symptoms appear [8].

Esophageal Motility Disorder
  • Pharyngo-esophageal motility disorders in Steinert’s myotonic dystrophy. Description of a case presenting with dysphagia. Pathologica, 84 (1992), pp. 523-530 [13.] I. Nonaka, O. Kobayashi, S. Osari.[elsevier.es]
Mediastinal Mass
  • The computerized tomography of chest revealed anterior mediastinal mass. The lymphocyte-rich thymoma was removed surgically and he received radiotherapy.[ncbi.nlm.nih.gov]
Prolonged PR Interval
  • A prolonged PR interval and QRS duration correlate with the degree of conduction delay between the atria and the bundle of His and between the bundle of His and the ventricles and with the distribution and extent of conduction-system lesions found at[nejm.org]
Third Degree Atrioventricular Block
  • Pacing equipment should also be readily available, as there have been reports of third-degree atrioventricular block refractory to atropine.[openanesthesia.org]
  • A total of 13.8% of patients developed sinus node dysfunction, 10% of patients had supraventricular arrhythmias, 5% had ventricular tachycardia, and 8.8% developed second- or third- degree atrioventricular block.[revespcardiol.org]
Abnormal ECG
  • Screening patients with myotonic dystrophy type 1 for signs and symptoms of heart failure, especially those with an abnormal ECG, is appropriate.[nejm.org]


Treatment regime for myotonic dystrophy involves a multidisciplinary approach. This is so because multiple organs and systems are affected by the disorder which indicates a team approach for effective management of the condition. In this, the primary role is that of the neurologist, who would recommend medications such as mexiletine to strengthen the muscles and improve the symptoms. Thereafter, treatment by cardiologists, ophthalmologist and pulmonologist would put in efforts to correct and manage various other symptoms.

Individuals in severe cases would require various mobility aids that include splints and ankle foot orthotics. Those with weakness in neck muscles would be given neck braces. Exercises would also be required to improve the gait of the individuals and the associated symptoms. Aerobic exercises using the stationary bicycle proved to be a safe an effective way for improving the fitness ability in patients with type 1 myotonic dystrophy [9].


Affected individuals who receive proper treatment can live a healthy life. The condition of myotonic dystrophy cannot be treated; however can be effectively managed with appropriate treatment regime to correct all the organs and systems that have been affected. In severe cases, individuals can lead a near to normal life with the help of physical aids and adaptive equipment for improvement in mobility.


The exact cause that triggers the development of myotonic dystrophy is not clearly known. However, genetic factors in an autosomal dominant pattern have been known to cause myotonic dystrophy. The condition is heredity in nature, and therefore individuals with a family history of myotonic dystrophy are likely to develop the same.

The gene involved in development of type 1 myotonic dystrophy is DMPK. Defective gene ZNF 9 on chromosome 3 gives rise to onset of myotonic dystrophy type 2. In this type of genetic defect, there is repetition of 4 nucleotides and such a pattern is termed as tetranucleotide repeat disorder [2].


Myotonic dystrophy type 1 is a much more common disorder than the type 2. The former type has a prevalence rate of 1 per 100,000 population in Japan. The condition has an estimated incidence rate of 3 to 15 per 100,000 in Europe [3]. Type 1 myotonic dystrophy most commonly strikes the pediatric population.

Sex distribution
Age distribution


Genetic defect is the major cause of myotonic dystrophy. The repeat in the nucleotide expands and enlarges with each generation, which in turn leads to earlier onset of disease with greater degree of severity.

The gene involved in development of type 1 myotonic dystrophy is DMPK. In this type, there is expansion of triplet repeat of gene cytosine-thymine and guanine. Individuals in whom there are more than 50 expansions exhibit significant signs and symptoms of the disease [4] [5].

The gene that is known to play foul in the causation of myotonic dystrophy type 2 is the ZNF9 on the chromosome 3. In this type, there is repetition of 4 nucleotides and therefore, the expansion is much larger than the type 1 myotonic dystrophy. The size of the expansion of repeated DNA makes no difference on the age of onset for individuals with type 2.


There is no way in preventing the genetic mutations that favor the onset of myotonic dystrophy. However, with the help of predictive testing, it is possible to tell whether an individual is at risk of developing such a type of disorder. It is though not possible to determine the age of onset of the disease. Prenatal diagnosis has provided some useful information regarding whether the fetus is at risk of developing myotonic dystrophy. This testing is carried out at 10 to 12 weeks of gestation through a method known as chorionic villus sampling [10].


Myotonic dystrophy essentially affects various body systems, giving rise to an array of debilitating symptoms. Myotonic dystrophy is of 2 types; namely: myotonic dystrophy type 1 and myotonic dystrophy type 2. The former type is also known as Steinert disease which majorly presents as a congenital disease, but it can affect the adult population too. The second type is a rare occurrence and is also termed as proximal myotonic dystrophy [1].

Patient Information

  • Definition: Myotonic dystrophy is a condition characterized by development of myotonia, endocrine changes, defects in the heart conduction and onset of cataracts. It is a chronic type of disorder which gradually progresses and produces debilitating symptoms.
  • Cause: Genetic defects are the major cause of myotonic dystrophy. The type of gene involved in type 1 and type 2 myotonic dystrophy include gene DMPK and gene ZNF 9 respectively. Individuals with family history of disorder are at an increased risk of falling prey to it.
  • Symptoms: Some of the common symptoms of myotonic dystrophy include weakness in hands and feet, myotonia, cataract, difficulty in swallowing and development of abnormal heart rhythms. In addition, affected individuals also complain of infertility, cognitive difficulties and sleepiness during daytime.
  • Diagnosis: Diagnostic procedures include a preliminary thorough physical checkup, followed by several laboratory studies, which involve blood tests, genetic testing, muscle biopsy and electrodiagnostic testing.
  • Treatment: Treatment involves a multidisciplinary approach as various organ systems are significantly affected. Primary role is that of neurologist who treats the muscle weakness with help of drug known as mexiletine



  1. Udd B, Krahe R. The myotonic dystrophies: molecular, clinical, and therapeutic challenges. Lancet Neurol 2012; 11:891.
  2. Day JW, Ricker K, Jacobsen JF, et al. Myotonic dystrophy type 2: molecular, diagnostic and clinical spectrum. Neurology 2003; 60:657.
  3. Bird, TD. Myotonic dystrophy type 1. Gene Reviews
  4. Fu YH, Pizzuti A, Fenwick RG Jr, et al. An unstable triplet repeat in a gene related to myotonic muscular dystrophy. Science 1992; 255:1256.
  5. Mahadevan M, Tsilfidis C, Sabourin L, et al. Myotonic dystrophy mutation: an unstable CTG repeat in the 3' untranslated region of the gene. Science 1992; 255:1253.
  6. Motta J, Guilleminault C, Billingham M, et al. Cardiac abnormalities in myotonic dystrophy. Electrophysiologic and histopathologic studies. Am J Med 1979; 67:467.
  7. Laberge L, Bégin P, Montplaisir J, Mathieu J. Sleep complaints in patients with myotonic dystrophy. J Sleep Res 2004; 13:95.
  8. Miller TM. Differential diagnosis of myotonic disorders. Muscle Nerve 2008; 37:293.
  9. Nguyen HH, Wolfe JT 3rd, Holmes DR Jr, Edwards WD. Pathology of the cardiac conduction system in myotonic dystrophy: a study of 12 cases. J Am CollCardiol 1988; 11:662.
  10. Harper, PS. Myotonic Dystrophy, 3rd Ed, WB Saunders, London 2001

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Last updated: 2019-07-11 21:26