There are at present two other distinct clinical muscle disorders associated with mutations in the sodium channel: hyperkalemic periodic paralysis and paramyotonia congenita. [jamanetwork.com]

Guidelines on clinical presentation and management of nondystrophic myotonias. [pubmed.ncbi.nlm.nih.gov]

The documents contained in this web site are presented for information purposes only. The material is in no way intended to replace professional medical care by a qualified specialist and should not be used as a basis for diagnosis or treatment. [orpha.net]

• Weakness

  Muscle weakness never occurred. Analysis of the contraction force of the flexor digitorum muscle showed a unique type of myotonia, namely, exercise-induced delayed-onset myotonia. [brain.unboundmedicine.com]

  Moxley Medicine 1997 A new clinical disorder that is similar to but distinct from myotonic dystrophy has emerged, and this new disorder does not appear to be linked to the genes for the sodium or chloride channels, and has cataracts, myotonia, weakness [semanticscholar.org]

  Episodic weakness is rare. Etiology Myotonia fluctuans is a sodium muscle channelopathy due to missense mutations of the SCN4A gene encoding the alpha subunit of the skeletal muscle voltage-gated sodium channel Nav1.4. [orpha.net]

• Pain

  —A 22-year-old woman gave a history of myotonia from the age of 9 years, at times causing painful spasms. The myotonia affected all her muscles, including the rectus abdominis muscle after sneezing. [jamanetwork.com]

  In acetazolamide-responsive myotonia, stiffness is often painful and myotonia is triggered by fasting and mildly by exercise and cold exposure. [orpha.net]

  […] congenital myotonia. 62 5 Wang DW...Bennett PB 10218481 1999 10 A novel muscle sodium channel mutation causes painful congenital myotonia. 62 5 Rosenfeld J...George AL 9392583 1997 11 Linkage of atypical myotonia congenita to a sodium channel locus. [malacards.org]

  Ten cases (8 kindreds) without mutations exhibited paramyotonia congenita with prominent pain and weakness. [n.neurology.org]

  Stomach pain, constipation, diarrhea, reflux and bloating. If you have hyperkalemic periodic paralysis, you may have paralysis episodes that last from one to four hours. [my.clevelandclinic.org]

• Episodic Weakness

  Episodic weakness is rare. Etiology Myotonia fluctuans is a sodium muscle channelopathy due to missense mutations of the SCN4A gene encoding the alpha subunit of the skeletal muscle voltage-gated sodium channel Nav1.4. [orpha.net]

• Sneezing

  The myotonia affected all her muscles, including the rectus abdominis muscle after sneezing. [jamanetwork.com]

• Diarrhea

  Stomach pain, constipation, diarrhea, reflux and bloating. If you have hyperkalemic periodic paralysis, you may have paralysis episodes that last from one to four hours. [my.clevelandclinic.org]

• Constipation

  Stomach pain, constipation, diarrhea, reflux and bloating. If you have hyperkalemic periodic paralysis, you may have paralysis episodes that last from one to four hours. [my.clevelandclinic.org]

• Muscle Weakness

  Muscle weakness never occurred. Analysis of the contraction force of the flexor digitorum muscle showed a unique type of myotonia, namely, exercise-induced delayed-onset myotonia. [brain.unboundmedicine.com]

  Muscle stiffness that gets better with activity, called a warm-up phenomenon. People with paramyotonia congenita and myotonic dystrophy type 2 don’t have this symptom. Pain. Weakness. [my.clevelandclinic.org]

  Unlike some other forms of myotonia, potassium-aggravated myotonia is not associated with episodes of muscle weakness. Frequency This condition appears to be rare; it has been reported in a small number of individuals and families worldwide. [medlineplus.gov]

• Myopathy

  G71.20 Congenital myopathy, unspecified G71.22 Centronuclear myopathy G71.220 X-linked myotubular myopathy G71.228 Other centronuclear myopathy G71.29 Other congenital myopathy G71.3 Mitochondrial myopathy, not elsewhere classified G71.8 Other primary [icd10data.com]

  In Japan, proximal myotonic myopathy, which is now called DM2 has not been reported. Both DM1 and DM2 have Cl channel abnormality which causes myotonia. [jstage.jst.go.jp]

  S 36081873 2022 23 Coexistence of Charcot-Marie-Tooth 1A and nondystrophic myotonia due to PMP22 duplication and SCN4A pathogenic variants: a case report. 62 Nan H...Wu L 34996390 2022 24 p.Asn1180Ile mutation of SCN4A gene in an Italian family with myopathy [malacards.org]

• Muscle Cramp

  […] contractions; fasciculation; hyporeflexia; muscle cramp; muscle weakness; hyperhidrosis; tachycardia; and myokymia. [icd10data.com]

  Your healthcare provider may prescribe a medication that blocks the sodium channel that’s on your muscle membrane. This can help with muscle cramps and stiffness. [my.clevelandclinic.org]

• Myalgia

  Myalgias and cramps are frequent. Intensity and topography of myotonic symptoms may vary. In myotonia fluctuans, episodes of stiffness vary in severity and frequency, and occur during the resting period following exercise. [orpha.net]

• Seizure

  Myotonia has been treated by various Na channel blockers, mexiletine, phenytoin, and carbamazepine, but they were originally developed for cardiac arrhythmia, or seizure disorders and they have undesirable side effects, weakness. [jstage.jst.go.jp]

• Excitement

  Channelopathies of skeletal muscle excitability. Cannon SC. Cannon SC. Compr Physiol. 2015 Apr;5(2):761-90. doi: 10.1002/cphy.c140062. Compr Physiol. 2015. PMID: 25880512 Free PMC article. Review. [pubmed.ncbi.nlm.nih.gov]

Management and Treatment How is myotonia treated? Treatments for myotonia are specific to each type: Dystrophic myotonias Treatment of dystrophic myotonias depends on the symptoms. [my.clevelandclinic.org]

Management and treatment Management of patients consists in medical therapy and avoidance of triggering factors (such as potassium-rich food). [orpha.net]

Myotonic Disorders in Childhood: Diagnosis and Treatment R. [semanticscholar.org]

[…] 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).[5170] For more [rarediseases.org]

Prognosis Prognosis is good with stability of symptoms during life but respiratory function may be compromised in severe myotonia permanens. The documents contained in this web site are presented for information purposes only. [orpha.net]

Outlook / Prognosis What can I expect if I have myotonia? The outlook for myotonia depends on how severe your symptoms are and whether you have other conditions. In particular, periodic paralyses can become worse with age. [my.clevelandclinic.org]

Etiology Myotonia fluctuans is a sodium muscle channelopathy due to missense mutations of the SCN4A gene encoding the alpha subunit of the skeletal muscle voltage-gated sodium channel Nav1.4. Genetic counseling Transmission is autosomal dominant. [orpha.net]

Summary Epidemiology Prevalence is unknown. Clinical description Fluctuating myotonia develops during childhood or adolescence and involves the extraocular, bulbar and limb muscles. Eyelid myotonia is often the first sign of the disease. [orpha.net]

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]