Abstract
RATIONALE: Long QT syndrome (LQTS) constitutes an inherited cardiac. Studies indicate that untreated LQTS carries a high mortality rate, and up to 20% of sudden infant death syndrome cases are associated with this condition. With active therapeutic intervention, the disease mortality rate can be reduced to 1%. PATIENT CONCERNS: We report a 10-year-old male patient who has a sudden loss of consciousness. The electrocardiogram showed the QT interval was prolonged, which means LQTS. The results of genetic testing found heterozygous mutations, c.1943 G > C, p.Gly 648 Ala in exon 7 of the KCNH2 gene, it was missing mutations and had not been reported before. DIAGNOSES: This patient was diagnosed with LQT interval syndrome based on the medical history, physical examination, electrocardiogram, and genetic testing. INTERVENTIONS: The patient was hospitalized for a duration of one week and received treatment comprising an oral β-blocker (propranolol: 2-4 mg·kg-1·d-1), potassium supplementation, and symptomatic management. No further syncopal episodes occurred. In the following year, the patient's QT interval on the electrocardiogram gradually returned to the normal range. The long-term prognosis requires continued monitoring. OUTCOMES: We provided a standard treatment plan for the child patient. So far, the child has not experienced fainting again, reducing the possibility of sudden death. LESSONS: We reported a new missense gene mutation that caused LQT2 syndrome. This case underscores the critical importance of early identification, diagnosis, and treatment of LQTS to significantly mitigate the risk of sudden death in children.