A significant minority of patients do present with a channelopathy like clinical presentation but have a negative genetic result for these established disease causing genes. [pn.bmj.com]

Guidelines on clinical presentation and management of nondystrophic myotonias. Muscle Nerve. 2020 Oct;62(4):430-444. doi: 10.1002/mus.26887. Epub 2020 May 27. Review. [medlineplus.gov]

Patients with myotonic dystrophy, in particular myotonic dystrophy type 2, may present with features of myotonia lacking overt weakness, mimicking the presentation of a non-dystrophic myotonic disorder. [now.aapmr.org]

Ophthalmoplegia as the presenting muscle-related manifestation of myotonic dystrophy. Rev Neurol. 2010;166(5):538-541. ↑ Versino M, Rossi B, Beltrami G, Sandrini G, Cosi V. Ocular motor myotonic phenomenon in myotonic dystrophy. [eyewiki.aao.org]

Muscle hypertrophy is less frequent than in myotonia congenita but in our recent series we found it to be present in ~30% of patients (Matthews et al., 2008b). [medscape.com]

• Multiple Congenital Anomalies

  A Novel De Novo Heterozygous SCN4a Mutation Causing Congenital Myopathy, Myotonia and Multiple Congenital Anomalies. [content.iospress.com]

• Respiratory Insufficiency

  Intensive care unit management Respiratory support Prevent metabolic complications Prevent muscle spasms Anti-spasm drugs Diazepam: Up to 20 mg q 2 to 6 hours Baclofen Neuromuscular blocking agents, if necessary Magnesium sulfate: If respiratory support [neuromuscular.wustl.edu]

  Double CMAP on single nerve stimuli ENG Quinidine, fluoxetine, Worsening with pyridostigmine AR CMS3C associated with AChR deficiency 616,323 Birth non-specific Neonatal hypotonia; ocular, episodic respiratory insufficiency, bulbar (swallowing), and proximal [mdpi.com]

  Most common symptoms of HYPERKALEMIC PERIODIC PARALYSIS Flexion contracture Skeletal muscle atrophy Gait disturbance Respiratory insufficiency Myopathy More info about HYPERKALEMIC PERIODIC PARALYSIS SOURCES: ORPHANET Alternate names HYPOKALEMIC PERIODIC [mendelian.co]

  The exception was a patient whose CK level rose to 3300 U/L in the context of a severe respiratory insufficiency due to influenza infection, for which she was admitted to hospital. [proquest.com]

  Noted DM1 symptoms which are considered less severe or common for DM2 are problems with smooth muscle (including G.I. symptoms), hypersomnia (daytime sleepiness), muscle wasting, dysphagia and respiratory insufficiency. [wikidoc.org]

• Dysphagia

  Some individuals with DM1 have difficulty swallowing (dysphagia). Dysphagia may result in aspiration pneumonia, an infection that develops when food, saliva and bacteria are inhaled into the lungs. [rarediseases.org]

  Treatment interruptions worsened myotonia and were associated with fatigue, pain, dysphagia, breathing difficulties, impaired digestion, and poor sleep quality. [emjreviews.com]

  Generalized spasms: May be more severe than in adults Fever Seizures Prognosis: Death (70%) unless agressive medical management Generalized type Most common form Onset Head & Neck often affected first: Dysphagia may be presenting symptom 33 Trismus: [neuromuscular.wustl.edu]

  Most common symptoms of PARAMYOTONIA CONGENITA OF VON EULENBURG Feeding difficulties Dysphagia Neonatal hypotonia Myalgia Muscle stiffness More info about PARAMYOTONIA CONGENITA OF VON EULENBURG SOURCES: ORPHANET Alternate names MYOTONIA, POTASSIUM-AGGRAVATED [mendelian.co]

• Muscle Rigidity

  The changed channel cannot properly adjust the ion flow, thereby increasing the movement of sodium ions into the skeletal muscle cells. The influx of excess sodium ions causes muscle contraction, which is a sign of muscle rigidity. [acroscell.creative-bioarray.com]

  If the rigidity includes the jaw muscles, intubation may be impossible.41 Suxamethonium can also induce hyperkalaemia and ventricular arrhythmia, which can be fatal.42 Emergency treatment for a myotonic crisis is with intravenous sodium channel blockers [pn.bmj.com]

  Stiffness Clinical features Muscle rigidity Face: Risus sardonicus Trunk Tetanic "spasms" Distribution: May be generalized Duration: May last second to minutes Stimuli: Noise; Touch; Movement Often painful "Spatula test": Spatula inserted into pharynx [neuromuscular.wustl.edu]

  rigidity and hyperthermia [130]. [mdpi.com]

  Both PMC and PAM cause repetitive APs and increase activity of the muscle leading to myotonia or muscle rigidity. [frontiersin.org]

Clinical Testing and Workup Molecular genetic testing can confirm a diagnosis of DM1 or DM2. Molecular genetic testing looks for changes or alterations in the DMPK gene known to cause DM1, or in the CNBP gene for DM2. [rarediseases.org]

Diagnostic workup The diagnosis of periodic paralysis can often be confirmed by genetic testing. This is recommended as the initial diagnostic step (after a careful history and exam) when there is adequate clinical suspicion. [medlink.com]

[…] be used to measure and monitor the effectiveness of drug treatment on symptoms over time. [emjreviews.com]

Treatment begins with avoiding foods that contain large amounts of potassium; other treatments may include physical therapy (stretching or massages to help relax muscles) or certain medications (such as mexiletine, carbamazapine, or acetazolamide). [rareguru.com]

K+, Treat thyroid condition Hours to days No No Yes During attacks ST depression, T wave flattens, U wave appears, sinus tachycardia Methimazole, Propranolol, K+, until anti–thyroid treatment, radio-iodine 131 or surgery Hypokalemic Periodic Paralysis [hkpp.org]

This can help in guiding symptom treatment and response. [pn.bmj.com]

Available or current treatment guidelines There are no FDA-approved therapeutic options for the treatment of myotonia or periodic paralysis. [now.aapmr.org]

Outlook / Prognosis What is the prognosis (outlook) for people with muscular dystrophy? Muscular dystrophy is a progressive disease. Symptoms get worse over time. [my.clevelandclinic.org]

Early predictions of outcomes A precise phenotypic and genotypic diagnosis is of critcal importance to provide prognosis, determine the most appropriate therapeutic intervention, and for accurate genetic counseling. [now.aapmr.org]

Myotonic dystrophy: prognosis and management. UpToDate, Inc. 2016 May 20. Available at: http://www.uptodate.com/contents/myotonic-dystrophy-treatment-and-prognosis Accessed: December 7, 2016. [rarediseases.org]

Prognosis and complications The long-term prognosis for these diseases is generally good. [medlink.com]

[…] exercise May be associated with paresthesias Lasts 15 to 60 minutes: Occasionally hours or days Provoked by Exercise Potassium loading Cold environment Pregnancy Glucocorticoids Stress Ethanol Fasting Relieved by: Carbohydrate intake; Mild exercise Prognosis [neuromuscular.wustl.edu]

In one study, ciliary body detachment was observed in all DM1 patients studied, suggesting a possible etiology for hypotony in this population.[12] Fuchs’ Endothelial Corneal Dystrophy The association between DM1 and Fuchs’ endothelial corneal dystrophy [eyewiki.aao.org]

Etiology Autosomal dominant and recessive myotonia congenita (MC) are associated with mutations of the chloride channel gene, CLCN1, in greater than 95% of cases. [now.aapmr.org]

Myotonic dystrophy: etiology, clinical features, and diagnosis. UpToDate, Inc. 2016 Mar 29. Available at: http://www.uptodate.com/contents/myotonic-dystrophy-etiology-clinical-features-and-diagnosis Accessed: December 7, 2016. Darras BT, Chad DA. [rarediseases.org]

Biological basis Etiology and pathogenesis Much of the recent progress in these disorders is the result of expression cloning and voltage-clamp studies in animal systems. [medlink.com]

A unique presentation and etiology of neonatal paradoxical vocal fold motion. Int J Pediatr Otorhinolaryngol. (2019) 125:199–200. doi: 10.1016/j.ijporl.2019.07.011 PubMed Abstract | CrossRef Full Text | Google Scholar 94. [frontiersin.org]

Other loci; Dominant 9 Epidemiology Most families: CAV3 mutation 1 family: 1q41 linkage CAV3 Genetics Caveolin-3 mutations: Missense R26Q: AD-RMD; HyperCKemia Asp27Glu: Variable phenotype, AD-RMD; Distal weakness; LGMD & Intrafamilial variation A45T: [neuromuscular.wustl.edu]

The Epidemiology of Neuromuscular Disorders: A Comprehensive Overview of the Literature. Journal of neuromuscular diseases 2015;2(1):73-85. Hughes MI, Hicks EM, Nevin NC, Patterson VH. [now.aapmr.org]

Epidemiology The prevalence of DM has previously been estimated in European populations at around 1 in 8000. [eyewiki.aao.org]

Epidemiology The prevalence of these disorders is not well defined. In general, these disorders are rare, probably affecting no more than 4 to 5 per 100,000 in the population. [medlink.com]

Epidemiology The frequency of MC was historically described as 1:23,000 for autosomal dominant MC (Thomsen disease) and 1:50,000 for autosomal recessive MC (Becker disease). [statpearls.com]

Miosis Miosis, usually evident as impaired pupillary dilation following administration of pharmacologic dilating agents, has been observed in DM patients.[9] Although the pathophysiology has not been fully elucidated, it has been theorized to be due to [eyewiki.aao.org]

Overview This article on periodic paralysis and related disorders introduces readers to the clinical presentations, basic concepts, and current understanding of the pathophysiology of these rare disorders or channelopathies. [medlink.com]

Channels active in the excitability of nerves and skeletal muscles across the neuromuscular junction: basic function and pathophysiology. [frontiersin.org]

No fasciculations or myokymia NCV: Mild reduction in SNAP & CMAP amplitudes in legs Nerve biopsy: Reduced number of Myelinated axons Familial Cramp Syndrome ● Autosomal Dominant Onset age: 10 to 15 years Cramps disappear after age 25 Serum CK: High Pathophysiology [neuromuscular.wustl.edu]

Defective Gating and Proteostasis of Human ClC-1 Chloride Channel: Molecular Pathophysiology of Myotonia Congenita. Front. Neurol. 2020, 11, 76. [mdpi.com]

Prevention How can I prevent muscular dystrophy? Unfortunately, there isn’t anything you can do to prevent getting muscular dystrophy. [my.clevelandclinic.org]

People with this disease will continue to show a continuous burst of muscle tension (muscle stiffness) that prevents the muscles from relaxing normally. [acroscell.creative-bioarray.com]

Beginning in childhood or adolescence, people with this condition experience episodes of sustained muscle tensing (myotonia) that prevent muscles from relaxing. Myotonia causes muscle stiffness that worsens after exercise. [medlineplus.gov]

Strong inward rectification prevents excess loss of K+ during the plateau phase of the cardiac action potential. [medlink.com]

At present many patients with minimal or manageable symptoms decline pharmacological treatment but it is possible that treatment may have a role in preventing subsequent myopathy. [medscape.com]