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Andersen-Tawil syndrome

MIM.170390

Tuesday 5 August 2008

The hallmark of the Andersen-Tawil syndrome (MIM.170390) is the triad of periodic paralysis (with variable serum potassium levels during an attack), cardiac arrhythmias, and dysmorphic features.

Distinctive physical findings include hypertelorism, micrognathia, low-set ears, high-arched or cleft palate, short stature, clinodactyly, syndactyly, and a broad nasal root.

Phenotypic expressivity is extremely variable, with patients exhibiting clinical evidence of two or three features of the triad each, with variable apparent severity. Rarely, individuals are asymptomatic carriers.

Andersen-Tawil syndrome is thought to be an autosomal-dominant disease with variable penetrance. Some cases are sporadic, and are caused by de novo mutations.

Two third of cases are caused by mutations of a widely expressed potassium channel encoded by the KCNJ2 gene, located on chromosome 17q. Complete evaluations of these patients require a cardiac assessment, because this disorder is part of the differential diagnosis of long QT syndrome. The remaining third of patients have an unknown molecular defect.

Treatment of this condition necessitates control of cardiac arrhythmias. If there is ventricular tachycardia, an implantable defibrillator was found to improve survival.

To decrease the frequency, severity, and duration of attacks, carbonic anhydrase inhibitors can also be used. Oral potassium can be used for the acute treatment of attacks as well as for prophylaxis, with the advantage of shortening the observed QT interval.

See also

- channelopathies