P387: Novel variant identified in the TET3 gene: A mother-daughter case that expands the phenotype of TET3-related disorders

Case Presentation: The proband is a 2-year-old full-term male with a history of poor weight gain, first noted at 3 months of age.Past medical history includes silent reflux, mild laryngomalacia, speech delay, and motor delay with delayed sitting and crawling, specifically.Denies seizures.Prenatal course and birth course were unremarkable.Birth weight 2.84 kg.His full sibling has ADHD and his mother has hypothyroidism.Physical exam was significant for a male appearing younger than the stated age with a thin build and triangular facies, non-verbal with delayed comprehension for age with truncal and axial hypotonia.Weight at the initial visit was 8.60 kg (0.12 percentile), length was 80 cm (14th percentile), and head circumference was 47 cm (22nd percentile).Diagnostic Workup: Negative genetic testing included CMA, Fragile X, CFTR, and Methylation RRSS/BWS.ES was positive for a De Novo Variant in PPP3CA p.(Glu282Lys) (GAA>AAA): c.844 G>A in exon 7 of the PPP3CA gene-pathogenic-Autosomal dominant.(NM_000944.4).This variant is consistent with neurodevelopmental disease with seizures.