What is it?

Andersen-Tawil syndrome is a rare genetic disorder characterized by episodes of muscle weakness and paralysis (periodic paralysis); abnormalities affecting the electrical system of the heart that can cause abnormal heart rhythms (arrhythmias); and a variety of distinctive facial and skeletal features. The specific symptoms and severity can vary greatly from one person to another, even among members of the same family. Some individuals will not develop all of the characteristic findings. Distinctive facial features may be so mild as to go unnoticed. In some cases, Andersen-Tawil syndrome is caused by mutations in the KCNJ2 gene; in other cases, the associated gene is unknown. The KCNJ2 gene mutation can occur randomly for unknown reasons (sporadically) or be inherited in an autosomal dominant manner.

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Additional names

This group contains additional names:
- Andersen syndrome
- Long QT syndrome 7

Signs & symptoms

Andersen-Tawil syndrome is defined by three main features, specifically periodic paralysis, arrhythmias and heart abnormalities, and distinctive physical features. However, the disorder is highly variable and not all affected individuals will develop all three of these characteristic symptoms. Andersen-Tawil syndrome can vary greatly in expression and severity from one person to another, even among members of the same family.


Because potassium levels may be reduced during an episode of periodic paralysis, a blood test to determine the serum potassium levels during an episode can be helpful in diagnosing the disorder in some cases.

Long exercise nerve conduction studies have been used to help diagnose individuals with Andersen-Tawil syndrome. During this test, an affected individual will perform voluntary muscle contractions of a small muscle on the ulnar side of the palm of the hand for approximately 2-5 minutes. This test allows physician to evaluate muscle function and specific results can be indicative of periodic paralysis.

An electrocardiogram or EKG records the heart’s electrical impulses and may reveal abnormal electrical patterns or activity commonly associated with Andersen-Tawil syndrome including prominent U waves, prolonged QU intervals, prolonged QT intervals, premature ventricular contractions, or polymorphic ventricular tachycardia.

Some individuals may undergo 24-Holter monitoring, during which an affected individual wears a small device for 24 hours. Through electrodes attached to the chest, this device continuously records the rhythm of the heart in order to detect the presence, frequency and duration of ventricular tachycardia and other symptoms.

Molecular genetic testing can confirm a diagnosis of Andersen-Tawil syndrome in some cases. Molecular genetic testing can detect mutations in the KCNJ2 gene known to cause the disorder, but is available only as a diagnostic service at specialized laboratories.


The treatment of Andersen-Tawil syndrome is directed toward the specific symptoms that are apparent in each individual. Treatment may require the coordinated efforts of a team of specialists. Pediatricians, neurologists experienced in the treatment of periodic paralysis, cardiologists experienced in the treatment of long QT syndrome, and other healthcare professionals may need to systematically and comprehensively plan an affect child’s treatment.

☝️ This is not a substitute for professional medical advice. Please consult with your physician before making any medical decision.

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