A pediatric case of Andersen-Tawil syndrome presenting with myalgia and elevated creatine kinase levels: A case report

Background Andersen-Tawil syndrome (ATS) is a rare, autosomal dominant disorder characterized by a triad of periodic paralysis, ventricular arrhythmias, and dysmorphic features. The diagnosis of ATS can be delayed if the initial symptoms, such as myalgia, are nonspecific. Early diagnosis is critical to prevent life-threatening cardiac complications. Case presentation A 14-year-old boy was referred for the evaluation of episodic myalgia, fatigue, and an incidentally elevated creatine kinase (CK) level. Based on the presence of characteristic facial features, a dental anomaly, and clinodactyly, along with a history of hypokalemic paralysis in the father, ATS was suspected. A long exercise test demonstrated a significant decrease in compound muscle action potential (CMAP) amplitude, suggesting periodic paralysis. Genetic testing identified a previously reported heterozygous variant, c.921G>A (p.Met307Ile), in KCNJ2 , confirming the diagnosis of ATS. Holter monitoring revealed ventricular arrhythmias. The same genetic variant and cardiac arrhythmias were identified in the patient's father and sister. Conclusion This case describes an atypical presentation of ATS with myalgia and elevated serum CK levels, which requires differentiation from muscular dystrophy. Careful attention to dysmorphic features and family history, along with electrophysiological testing, is useful for early diagnosis. The recognition of atypical presentations is essential for initiating appropriate cardiac surveillance and preventing potentially fatal outcomes.