Lethal Transaldolase Deficiency Mimicking Gestational Alloimmune Liver Disease: Prenatal Sonography and Identification of a Novel TALDO1 Variant

• Objective: To describe the prenatal sonographic and neonatal features of two siblings with lethal transaldolase deficiency and highlight its phenotypic overlap with gestational alloimmune liver disease (GALD). • Study Design: Retrospective review of consecutive pregnancies in a single family, analyzing sequential prenatal ultrasound surveillance, maternal therapeutic interventions, neonatal clinical course, and post-mortem trio exome sequencing. • Results: Both siblings exhibited severe early-onset fetal growth restriction, echogenic bowel, neonatal hemochromatosis, and hypertrophic cardiomyopathy. Because the clinical presentation during the first pregnancy closely mimicked GALD, the second pregnancy was treated empirically with intravenous immunoglobulin (IVIG), which proved entirely ineffective. Subsequent exome sequencing revealed compound heterozygous variants in the TALDO1 gene, including a novel pathogenic variant (p.Arg239Cys). These findings demonstrate that the hepatic pathology in transaldolase deficiency is a primary metabolic process rather than an antibody-mediated alloimmune process. • Conclusion: Transaldolase deficiency should be considered in the differential diagnosis for fetuses presenting with unexplained severe growth restriction accompanied by echogenic bowel or hepatic echogenicities, or in neonates with fulminant liver failure, particularly when associated with cardiomyopathy. This case highlights the value of performing prenatal exome sequencing prior to initiating targeted therapies like IVIG. Establishing a definitive genetic diagnosis prevents the utilization of futile, resource-intensive treatments, optimizing patient care and prognostic counseling