Andersen Tawil syndrome

Andersen-Tawil syndrome
Other names	Long QT syndrome type 7
Specialty	Cardiology, Neurology, Genetics
Symptoms	Periodic paralysis, cardiac arrhythmias, dysmorphic features
Usual onset	Childhood
Duration	Lifelong
Causes	Mutations in the KCNJ2 gene
Diagnostic method	Clinical evaluation, genetic testing
Treatment	Symptomatic management, beta-blockers, pacemakers
Prognosis	Variable
Frequency	Rare

Andersen-Tawil syndrome (ATS), also known as Long QT syndrome type 7, is a rare genetic disorder characterized by a triad of symptoms: periodic paralysis, cardiac arrhythmias, and distinctive facial and skeletal features. It is an autosomal dominant condition caused by mutations in the KCNJ2 gene, which encodes the inward rectifier potassium channel Kir2.1.

Clinical Features

Patients with Andersen-Tawil syndrome typically present with a combination of the following features:

Periodic Paralysis

Episodes of muscle weakness or paralysis, often triggered by factors such as rest after exercise, fasting, or stress. These episodes can vary in frequency and severity.

Cardiac Arrhythmias

Individuals may experience ventricular arrhythmias, including ventricular tachycardia and ventricular fibrillation, which can lead to syncope or sudden cardiac death. The ECG may show a prolonged QT interval.

Dysmorphic Features

Characteristic facial features may include a broad forehead, low-set ears, and a small jaw. Skeletal abnormalities such as scoliosis or clinodactyly may also be present.

Genetics

Andersen-Tawil syndrome is caused by mutations in the KCNJ2 gene located on chromosome 17q24.3. This gene encodes the Kir2.1 potassium channel, which is crucial for maintaining the resting membrane potential in muscle and cardiac cells. Mutations lead to dysfunctional ion channels, resulting in the clinical manifestations of the syndrome.

Diagnosis

Diagnosis is based on clinical evaluation, family history, and genetic testing. The presence of the triad of symptoms, along with a positive genetic test for KCNJ2 mutations, confirms the diagnosis.

Management

Management of Andersen-Tawil syndrome is symptomatic and may include:

• Beta-blockers: To manage cardiac arrhythmias and reduce the risk of sudden cardiac death.
• Pacemakers or Implantable Cardioverter-Defibrillators (ICDs): For patients with significant arrhythmias.
• Potassium supplements: To prevent or treat episodes of periodic paralysis.
• Lifestyle modifications: Avoiding triggers such as fasting and strenuous exercise.

Prognosis

The prognosis of Andersen-Tawil syndrome is variable and depends on the severity of cardiac involvement. With appropriate management, many individuals can lead relatively normal lives.

Epidemiology

Andersen-Tawil syndrome is a rare condition, with an estimated prevalence of less than 1 in 1,000,000 individuals. It affects both males and females equally.

History

The syndrome was first described by Ellen Andersen in 1971 and further characterized by Rabi Tawil in 1994, leading to its current name.

Also see

• Long QT syndrome
• Periodic paralysis
• Cardiac arrhythmia
• Genetic disorders