Andersen-Tawil Syndrome
OVERVIEW
Andersen-Tawil syndrome is a disorder that causes episodes of muscle weakness (periodic paralysis), changes in heart rhythm (arrhythmia), and developmental abnormalities. Periodic paralysis begins early in life, and episodes last from hours to days. These episodes may occur after exercise or long periods of rest, but they often have no obvious trigger. Muscle strength usually returns to normal between episodes. However, mild muscle weakness may eventually become permanent.
SYMPTOMS
Andersen-Tawil syndrome (ATS) is characterized by a triad of: episodic flaccid muscle weakness (i.e., periodic paralysis); ventricular arrhythmias and prolonged QT interval; and anomalies including low-set ears, widely spaced eyes, small mandible, fifth-digit clinodactyly, syndactyly, short stature, and scoliosis.
Causes
Mutations in the KCNJ2 gene cause about 60 percent of all cases of Andersen-Tawil syndrome. When the disorder is caused by mutations in this gene, it is classified as type 1 (ATS1).
The KCNJ2 gene provides instructions for making channels that transport positively charged potassium ions across the membrane of muscle cells. The movement of potassium ions through these channels is critical for maintaining the normal function of muscles used for movement (skeletal muscles) and cardiac muscle. Mutations in the KCNJ2 gene alter the usual structure and function of these potassium channels. 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 determined the role of the KCNJ2 gene in bone development, and it is not known how mutations in the gene lead to the skeletal changes and other physical abnormalities often found in Andersen-Tawil syndrome.
In the 40 percent of cases not caused by KCNJ2 gene mutations, the cause of Andersen-Tawil syndrome is usually unknown. These cases are classified as type 2 (ATS2). Studies suggest that variations in at least one other potassium channel gene may underlie the disorder in some of these affected individuals.
DIAGNOSIS
Andersen–Tawil syndrome (ATS) is a rare ion channel disorder characterized by the clinical triad of periodic paralysis, ventricular arrhythmias associated with long QT and skeletal developmental anomalies. A diagnosis of ATS can be made when an individual exhibits two of these three cardinal features.
TREATMENT
Treatment. As a genetic condition, Andersen–Tawil syndrome cannot be cured. However, many of symptoms of Andersen–Tawil such as blackouts due to abnormal heart rhythms or periodic paralysis can be successfully treated with medication or implantable devices.
TYPE OF DOCTOR AND DEPARTMENT: NEUROLOGY SPECIALIST CAN DIAGNOSES THIS DISEASE.
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