Thyroid hormone metabolism defect due to compound heterozygous <i>SECISBP2</i> mutations: first reported case in Korea

This case broadens the mutational spectrum of <i>SECISBP2</i>-related THMD and demonstrates its multisystemic nature, including auditory and possible ocular involvement. Despite biochemical improvement, neurodevelopmental outcomes remained poor, emphasizing tissue-specific T3 deficiency and the limited efficacy of current therapy. Early recognition and molecular diagnosis are crucial for timely management and long-term follow-up.