6492 Novel compound heterozygous mutations in the SBP2 gene

Abstract Disclosure: H. Jeong: None. Mutations in the selenocysteine insertion sequence binding protein 2 gene (SECISBP2 also known as SBP2) result in a multisystemic disorder. A 4-year-old Korean girl presented with atypical thyroid function test result, characterized by normal TSH 2.13 μIU/mL, decreased T3 0.51 ng/mL, free T3(FT3) 1.71 (pg/mL), and elevated free thyroxine (FT4) 4.28 ng/dL. Additionally, she exhibited short stature below 2 standard deviations and delayed bone age. She has not yet begun speaking, and her waking ability commenced only recently. She conceived twins through natural pregnancy, but tragically, her twin sibling passed away in utero at 8 weeks of gestation.A targeted next-generation sequencing panel revealed compound heterozygous mutation in SBP2 gene (p.Arg120Ter/p.Arg672Ter) and in TPO gene (p.Glu413Gln).Her serum selenium level was relatively low,, easuring at 6.94 ng/dL. She underwent T3 supplementation and received a daily selenium supplement of 20mcg. Subsequently, her thyroid function tests normalized. Presentation: 6/2/2024