Andersen Tawil syndrome – a case study

Abstract

The first case of a patient with periodic paralysis of muscles accompanied by ventricular arrhythmias was described in 1963 by Klein and colleagues[1]. In 1971, the team led by E.D. Andersen published a paper on the familial coexistence of neurological disorders and arrhythmias accompanied by dysmorphic features, suggesting a new, unclassified disease syndrome [2]. Another report, this time by the Tawil team, analized 10 cases described up to the time and 4 new diagosed by him, giving the genetic basis for understanding the mechanisms of the disease inheritance [3]. In 2003, the syndrome described by Tawilla was named after Andersen and Tawill (Andersen Tawil Syndrome - ATS).

ATS (syn. long QTc syndrome, type 7, LQTS 7,) is a rare genetic disorder inherited in an autosomal dominant manner. So far around 200 diagnoses of ATS have been made in the world. Mutations in the KCNJ2 gene located on the long arm of chromosome 17, encoding the Kir 2.1 protein, are responsible for the disease subtype 1, which accounts for 60% of the described cases. This protein is a component of the potassium ion channel, and its abnormal structure and function is the cause of repolarization disorders in the cells of the heart and skeletal muscles. However, in 6-20% of patients from families with confirmed presence of KCNJ2 mutations, no clinical symptoms of the syndrome were reported. It proves its differentiated penetration, and the genetic mechanism in the remaining patients remains unknown.

Despite the fact that patients with ATS are a very heterogeneous group in terms of the observed symptoms, this syndrome has a classic triad:

1. changes in the ECG trace of the T wave and the presence of the U wave (extended duration of the descending arm of the T wave, a characteristic wide U wave and a wide combination of T and U waves - these features distinguish ATS from other long QTc syndromes) and arrhythmias in the form of single multifocal premature ventricular beats, polymorphic, bidirectional ventricular tachycardia, which may be asymptomatic or, more often, cause palpitations. Less common manifestations of arrhythmias are fainting, cardiac arrest and sudden cardiac death[4].

2. periodic muscle strenght impairment (periodic paralysis) occurring most often after a prolonged period of rest or during rest after intense exercise, accompanied by a decrease in the concentration of potassium in the blood serum; in some cases, there is a constant, albeit slight, weakening of muscle strength

3. typical malformations (dysmorphia), most often including short stature, hypertelorism, small mandible, low-set auricles and abnormalities of curvature within the spine.

In patients with an unconfirmed genetic mutation, the diagnosis of ATS requires at least two of the above-mentioned symptoms. However, in some genetically confirmed cases their expression may be very low[5]

Due to the described dysfunctions in the cognitive sphere, mainly in the field of reading skills and mathematical skills, patients should also be covered by psychological care, and due to behavioral changes, in some cases also psychiatric.