4986LQTS type 7 evaluation in patient presenting with neurological signs: weakness and periodic paralyses of lower extremities

Abstract

Introduction: Long QT syndrome (LQTS) is a large group of channelopathies. We provide a case of 12-year-old male with rare LQTS type 7 or Andersen-Tawil syndrome (ATS). Case report description: Firstly our patient showed up to neurologist with muscle weakness and paresthesia in lower limbs with an inability to walk properly. After the routine ECG signs of QT prolongation was found and he was send to cardiologist. On the resting ECG U-wave and QUc-568ms appeared with single episodes of polymorphic ventricular premature beats detected by Holter. Echo and treadmill stress test showed no significant pathological abnormalities. There were no registered syncopes. Physical examination showed several face and skeletal dysmorphic features as, for example, broad forehead, micrognathia and clinodactyly of fourth fingers. The nervous system examination revealed weakness of proximal limb muscles (MRC grade 4 on the right and MRC grade 3 on the left) in both lower limbs with pyramidal signs of foot clonus. Description of the techniques used: We provided a complete diagnostic examination: ECG, 24-hour Holter monitor, Echo, treadmill stress test, EEG, thyroid gland ultrasound, thyroid hormones measurements, blood electrolyte levels. Questions and possible differential diagnosis: The main objective was to distinguish exact type of LQTS and to choose correct management. The controversial question was the selection of proper pharmacological rhythm control therapy and assessment of the necessity of ICD in asymptomatic patient. The second significant aim was to find a way how to cope with periodic paralysis. Finding the connection between the type of LQTS and response to treatment either to risk of SCD, seems to be of paramount importance. The possible differential diagnosis included other LQTS types, ventricular arrhythmias and periodic paralyses of hypokaliemic, hyperkaliemic or thyrotoxic nature. Answers and discussion: Performed genetic testing detected heterozygous mutation in KCNJ2 that proves the ATS diagnosis suspected clinically. Paralysis attacks were not connected with potassium or calcium imbalance according to daily electrolyte monitoring. Paralysis developed after physical training as well as after long rest. No other specific trigger (as electrolyte imbalance, thyroid function abnormality etc) was detected. Commonly paralyses lasted from several hours to days and disappeared spontaneously. After detailed literature search and delicate evaluation of patient's family history (two cases of SCD in close relatives) the heart team decided to start rhythm control therapy with selective beta-blocker (atenolol in 1 mg/kg/per day). After two days of atenolol treatment U wave was no longer detected and QTc was in reference range (figure B). Patient's ECG pattern was normal in consecutive half year follow-up period. Unfortunately the nature of periodic paralyses remains unknown and patient still shows episodes of periodic weakness. Conclusions and implications for clinical practice: Even though SCD beeing not common in patients with ATS, the electric myocardium instability and burdened family history make patient to fall in a high-risk group. To conclude we suggest the multidisciplinary team of specialists (pediatrician, neurologist, cardiologist, geneticist, cardiovascular surgeon) is becoming increasingly important in early diagnosis and maintenance of patients with ATS.