Andersen-Tawil syndrome

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Vamsikrishna Gunnam M.B.B.S [2]

Andersen-Tawil syndrome (ATS) is a very rare syndrome which is characterized by periodic paralysis, arrhythmias and long QT interval. Ellen Andersen was the first to describe the Andersen-Tawil syndrome (ATS) in 1971.

Andersen–Tawil syndrome may be classified according to genetic mutations into two groups: Type 1 Andersen–Tawil syndrome and type 2 Andersen–Tawil syndrome.

It is understood that Andersen-Tawil syndrome is the result of mutation in KCNJ2 gene which encodes for Kir2.1 inward rectifier potassium channel that involves in cardiac repolarization phase. 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. Andersen-Tawil syndrome is a rare syndrome transmitted in autosomal dominant pattern.

Genes involved in the pathogenesis of Andersen-Tawil syndrome include KCNJ2 gene, KCNJ5 gene and an unknown gene.

Andersen-Tawil syndrome must be differentiated from Romano-Ward syndrome, Timothy syndrome, Jervell and Lange-Nielsen syndrome (JLNS), Brugada syndrome, Sudden infant death syndrome (SIDS), Hypokalemic periodic paralysis, Hyperkalemic periodic paralysis and Thyrotoxic periodic paralysis.

Andersen-Tawil syndrome is a rare hereditary multisystem disorder transmitted in autosomal dominant pattern. Only 200 cases of Andersen-Tawil syndrome were reported worldwide.

Risk factors in Andersen-Tawil syndrome include a family member who is having KCNJ2 gene mutation.

There is insufficient evidence to recommend routine screening for Andersen-Tawil syndrome. But when a patient with positive KCNJ2 mutation follow the patient with ECG and holter monitoring.

If left untreated, patients with Andersen-Tawil syndrome may progress to develop periodic paralysis, cardiac arrhythmias and can lead to the death of the patient. Common complications of Andersen-Tawil syndrome include neuromuscular symptoms and malignant hyperthermia. Prognosis is generally range from good to poor.

The diagnosis of Andersen-Tawil syndrome (ATS) is suspected in individuals whose satisfies either criteria A and criteria B with molecular genetic testing to confirm.

Patients with Andersen-Tawil Syndrome may have a positive history of periodic paralysis, cardiac symptoms, ventricular arrhythmias and common symptoms syncope, muscular weakness and Skeletal developmental abnormalities

Patients with Andersen-Tawil syndrome usually appear shorter than normal. Physical examination of patients with Andersen-Tawil syndrome is usually remarkable for hypoplastic mandible, micrognathia, broad nose, low set ears and clinodactyly.

Laboratory findings consistent with the diagnosis of Andersen-Tawil syndrome (ATS) include serum potassium levels. Some patients with Andersen-Tawil syndrome(ATS) may have elevated/reduced concentration of serum potassium levels, which is usually suggestive of Andersen-Tawil syndrome (ATS).

An ECG may be very helpful in the diagnosis of Andersen-Tawil Syndrome. Findings on an ECG diagnostic of Andersen-Tawil Syndrome include a long QTc (LQT) interval, U waves, wide T-U junction and T-waves.

There are no x-ray findings associated with Andersen-Tawil syndrome.

There are no ultrasound findings associated with Andersen-Tawil syndrome.

There are no CT scan findings associated with Andersen-Tawil syndrome.

There are no MRI scan findings associated with Andersen-Tawil syndrome.

There are no other imaging findings associated with Andersen-Tawil syndrome.

There are no other diagnostic findings associated with Andersen-Tawil syndrome.

There is no treatment for Andersen-Tawil Syndrome; the mainstay of therapy is to treat the symptoms and manage the patient. Potassium levels plays an important role in the management of the symptoms.

Surgical intervention is not recommended for the management of Andersen-Tawil syndrome (ATS).

Effective measures for the primary prevention of Andersen-Tawil syndrome (ATS) include Lifestyle modifications, carbonic anhydrase inhibitors using, potassium supplements and cardioverter-defibrillator.

Effective measures for the secondary prevention of Andersen-Tawil syndrome (ATS) include avoidance of some antiarrhythmic drugs and anesthetic precautions.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Vamsikrishna Gunnam M.B.B.S [2]

Andersen-Tawil syndrome (ATS) is a very rare syndrome which is characterized by periodic paralysis, arrhythmias and long QT interval. Ellen Andersen was the first to describe the Andersen-Tawil syndrome (ATS) in 1971.

• In 1971, Ellen Andersen et al was the first to report the symptoms of the syndrome which includes short stature, hypertelorism, broad nasal root, mandibular hypoplasia, scaphocephaly, and clinodactyly in an 8 year old boy.^[1][2]
• In 1976, Stubbs described bidirectional ventricular tachycardia in a women.
• In 1977, Sansone et al reported the symptoms of periodic paralysis, ventricular arrhythmia in a patient.
• In 1994, Tawil gave the name Andersen syndrome for a clinical triad which consists of periodic paralysis, ventricular ectopy, and dysmorphic features.
• In 1994, Tawil made a significant contributions to the understanding that Andersen’s syndrome is different from other long QT syndrome demonstrating lack of genetic linkage.^[3]
• In 2002, Andelfinger et al identified missense mutation in KCNJ2 gene were first implicated in the pathogenesis of Andersen-Tawil syndrome.

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Vamsikrishna Gunnam M.B.B.S [2]

It is understood that Andersen-Tawil syndrome is the result of mutation in KCNJ2 gene which encodes for Kir2.1 inward rectifier potassium channel that involves in cardiac repolarization phase. 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. Andersen-Tawil syndrome is a rare syndrome transmitted in autosomal dominant pattern.

• It is understood that Andersen-Tawil syndrome is the result of mutation in KCNJ2 gene.^[1][2][3]
• KCNJ2 gene encodes for Kir2.1 inward rectifier potassium channel which is a component of the inward rectifier IK1 and involves in repolarizing current during the late phase of repolarization and plays an important role in controlling the diastolic membrane potential of the cardiac membrane.^[4][5]
• The protein encoded by the KCNJ2 gene which is Kir2.1 inward rectifier potassium channel transports potassium ions into muscle cells.
• The movement of Kir2.1 inward rectifier potassium channel ions is very crucial in maintaining the normal functions of skeletal muscles which are used for movement and cardiac muscle.
• Any change in the Kir2.1 inward rectifier potassium channel ions transport especially in the heart leads to abnormal heart rhythm which will result in arrhythmia and long QT or QU syndrome.^[6]
• Any change in the Kir2.1 inward rectifier potassium channel ions transport in skeletal muscles leads to periodic paralysis and and developmental abnormalities.^[7]

• Andersen-Tawil syndrome is transmitted in autosomal dominant pattern.

• Genes involved in the pathogenesis of Andersen-Tawil syndrome include:^{[8][9][10][11]}
  • KCNJ2 gene in 60% of the cases Andersen-Tawil syndrome (ATS) 1 type
  • Unknown gene defect in 40% of the cases of Andersen-Tawil syndrome (ATS) 2 type
  • KCNJ5 gene is also implicated but no cases reported in Andersen-Tawil syndrome

Conditions associated with Andersen-Tawil syndrome include:^[12][13]

• Episodes of flaccid paralysis
• Ventricular arrhythmias
• Dilated cardiomyopathy
• Unique physical features

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Vamsikrishna Gunnam M.B.B.S [2]

Andersen-Tawil syndrome must be differentiated from Romano-Ward syndrome, Timothy syndrome, Jervell and Lange-Nielsen syndrome (JLNS), Brugada syndrome, Sudden infant death syndrome (SIDS), Hypokalemic periodic paralysis, Hyperkalemic periodic paralysis and Thyrotoxic periodic paralysis.

• Andersen-Tawil syndrome must be differentiated from the following diseases:^{[1][2][3][4][5][6][7]}
  • Romano-Ward syndrome
  • Timothy syndrome
  • Jervell and Lange-Nielsen syndrome (JLNS)
  • Brugada syndrome
  • Sudden infant death syndrome (SIDS)
  • Hypokalemic periodic paralysis
  • Hyperkalemic periodic paralysis
  • Thyrotoxic periodic paralysis

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Vamsikrishna Gunnam M.B.B.S [2]

Andersen-Tawil syndrome is a rare hereditary multisystem disorder transmitted in autosomal dominant pattern. Only 200 cases of Andersen-Tawil syndrome were reported worldwide.

• The incidence of Andersen-Tawil syndrome is approximately less than 1 per 100,000 individuals worldwide.^[1]
• Only 200 cases of Andersen-Tawil syndrome were reported worldwide.
• Patients who are suffering with periodic paralysis Andersen-Tawil syndrome only accounts for less than 10% of these patients.

• The exact prevalence of Andersen-Tawil syndrome is unknown.
• The prevalence of congenital Long QT syndrome(LQTS) is around 1 in 2000 births.^[2]

• Andersen-Tawil syndrome commonly affects individuals of younger age, most commonly in the first decade of life younger than 10 years.

• There is no racial predilection to Andersen-Tawil syndrome as of now.

• Andersen-Tawil syndrome affects men and women equally.

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Vamsikrishna Gunnam M.B.B.S [2]

There is insufficient evidence to recommend routine screening for Andersen-Tawil syndrome. But when a patient with positive KCNJ2 mutation follow the patient with ECG and holter monitoring.

• There is insufficient evidence to recommend routine screening for Andersen-Tawil syndrome.
• But when a patient with positive KCNJ2 mutation and have no symptoms in Andersen-Tawil syndrome yearly screening with the following should be considered:
  • A 12-lead ECG^[1][2][3]
  • 24-hour Holter monitoring

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Vamsikrishna Gunnam M.B.B.S [2]

If left untreated, patients with Andersen-Tawil syndrome may progress to develop periodic paralysis, cardiac arrhythmias and can lead to the death of the patient. Common complications of Andersen-Tawil syndrome include neuromuscular symptoms and malignant hyperthermia. Prognosis is generally range from good to poor.

• The symptoms of Andersen-Tawil syndrome usually develop in the first decade of life, and start with symptoms such as episodic flaccid muscle weakness, ventricular arrhythmias and prolonged QT interval.^[1][2]
• If left untreated, patients with Andersen-Tawil syndrome may progress to develop cardiac arrhythmias and can lead to the death of the patient.

• Common complications of Andersen-Tawil syndrome include:^{[3][4][5][6][7][8]}
  • Syncope or presyncopal attacks
  • Exercise-induced nonsustained bidirectional ventricular tachycardia
  • QT or QU prolongation with polymorphic ventricular tachycardia which are life-threatening
  • Sudden cardiac death
  • Neurological or neurocognitive defects

• Prognosis is generally range from good to poor, based on the severity of the mutation on KCNJ2 gene.

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