Andersen–Tawil syndrome

Andersen–Tawil syndrome
Synonyms Cardiodysrhythmic potassium-sensitive periodic paralysis
This condition affects the QT interval(in blue)
Specialty Cardiology Edit this on Wikidata

Andersen–Tawil syndrome, also called Andersen syndrome and Long QT syndrome 7, is a form of long QT syndrome.[1] It is a rare genetic disorder, and is inherited in an autosomal dominant pattern and predisposes patients to cardiac arrhythmias. Jervell and Lange-Nielsen syndrome is a similar disorder which is also associated with sensorineural hearing loss. It was first described by Ellen Damgaard Andersen.

Signs and symptoms

A triad of hypokalemic periodic paralysis, potentially fatal cardiac ventricular ectopy and characteristic physical features is known as Anderson-Tawil Syndrome. It affects the heart, symptoms are a disruption in the rhythm of the heart's lower chambers (ventricular arrhythmia) in addition to the symptoms of long QT syndrome. There are also physical abnormalities associated with Andersen–Tawil syndrome, these typically affect the head, face, and limbs. These features often include an unusually small lower jaw (micrognathia), low-set ears, and an abnormal curvature of the fingers called clinodactyly. Furthermore, it causes symptoms which are similar to Long QT syndrome.

Long QT syndrome, a hereditary disorder that usually affects children or young adults, slows the signal that causes the ventricles to contract. Another electrical signal problem, atrial flutter, happens when a single electrical wave circulates rapidly in the atrium, causing a very fast but steady heartbeat. Heart block involves weak or improperly conducted electrical signals from the upper chambers that can't make it to the lower chambers, causing the heart to beat too slowly. These conditions can increase the risk for cardiac arrest. Treatment may include medication, ablation, or an implanted device to correct the misfiring, such as a pacemaker or defibrillator. Typical physical abnormalities seen in people with Andersin-Tawil syndrome may include:

  • Widely spaced eyes (hypertelorism)
  • Short stature
  • Scoliosis
  • Webbed toes or fingers
  • Unusual short fingers
  • Low set ears
  • Broad forehead
  • Small jaw
  • Protruding jaw
  • Broad nasal root
  • Clinodactyly

Some more severe issues can be caused via the potassium channelopathy. These include paralysis (mostly temporary and can last from several seconds to several minutes), inability to perform long distance/interval exercises and sudden exhaustion- although this can be a sign of cardiac arrhythmia- which should be immeditaley checked out by a GP, whether you have been diagnosed with ATS or not.

Cause

This condition is incredibly rare, with only 100 cases reported worldwide, however there are thought to be many cases that have been left undiagnosed. It is either inherited from at least one parent containing the mutated gene. or it can be gained through the mutation of the KCNJ2 gene.

Diagnosis

  • Prolongation of QT interval
  • Cardiac arrhythmias
  • Weakness: attacks or permanent

Type 1 and type 2

Cardiac muscle

Two types of Andersen–Tawil syndrome are distinguished by their genetic causes.

  • Type 1, which accounts for about 60 percent of all cases of the disorder, is caused by mutations in the KCNJ2 gene.[2][3][4]
  • The remaining 40 percent of cases are designated as type 2; the cause of the condition in these cases is unknown.

The protein made by the KCNJ2 gene forms a channel that transports potassium ions into muscle cells. The movement of potassium ions through these channels is critical for maintaining the normal functions of skeletal muscles which are used for movement and cardiac muscle. Mutations in the KCNJ2 gene alter the usual structure and function of potassium channels or prevent the channels from being inserted correctly into the cell membrane. Many mutations prevent a molecule called PIP2 from binding to the channels and effectively regulating their activity. These changes disrupt the flow of potassium ions in skeletal and cardiac muscle, leading to the periodic paralysis and irregular heart rhythm characteristic of Andersen–Tawil syndrome. Researchers have not yet determined the role of the KCNJ2 gene in bone development, and it is not known how mutations in the gene lead to the developmental abnormalities often found in Andersen–Tawil syndrome.

Eponym

It is named for Ellen Andersen[5] and Rabi Tawil.[6][7]

References

  1. ↑ Statland, Jeffrey M.; Tawil, Rabi; Venance, Shannon L. (1993-01-01). Pagon, Roberta A.; Adam, Margaret P.; Ardinger, Holly H.; Wallace, Stephanie E.; Amemiya, Anne; Bean, Lora JH; Bird, Thomas D.; Ledbetter, Nikki; Mefford, Heather C., eds. GeneReviews(®). Seattle (WA): University of Washington, Seattle. PMID 20301441. update 2015
  2. ↑ Tristani-Firouzi M, Jensen JL, Donaldson MR, et al. (2002). "Functional and clinical characterization of KCNJ2 mutations associated with LQT7 (Andersen syndrome)". J. Clin. Invest. 110 (3): 381–8. doi:10.1172/JCI15183. PMC 151085. PMID 12163457.
  3. ↑ Pegan S, Arrabit C, Slesinger PA, Choe S (2006). "Andersen's syndrome mutation effects on the structure and assembly of the cytoplasmic domains of Kir2.1". Biochemistry. 45 (28): 8599–606. doi:10.1021/bi060653d. PMID 16834334.
  4. ↑ Kim, JB; Chung, KW (December 2009). "Novel de novo Mutation in the KCNJ2 Gene in a Patient With Andersen-Tawil Syndrome". Pediatric Neurology. 41 (6): 464–466. doi:10.1016/j.pediatrneurol.2009.07.010. PMID 19931173.
  5. ↑ Andersen ED, Krasilnikoff PA, Overvad H (1971). "Intermittent muscular weakness, extrasystoles, and multiple developmental anomalies. A new syndrome?". Acta Paediatrica Scandinavica. 60 (5): 559–64. doi:10.1111/j.1651-2227.1971.tb06990.x. PMID 4106724.
  6. ↑ Tawil R, Ptacek LJ, Pavlakis SG, et al. (1994). "Andersen's syndrome: potassium-sensitive periodic paralysis, ventricular ectopy, and dysmorphic features". Ann. Neurol. 35 (3): 326–30. doi:10.1002/ana.410350313. PMID 8080508.
  7. ↑ synd/3410 at Who Named It?
Classification
External resources
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