ALG8-CDG: Advances in Molecular and Prenatal Phenotyping Facilitate Prenatal Diagnosis and Genetic Counseling.

Background: ALG8-congenital disorder of glycosylation (ALG8-CDG) is a rare inherited metabolic disorder leading to severe multisystem manifestations, with no reported prenatal patients to date.

Methods: We describe two fetuses from a single family with ALG8-CDG presenting with prenatal hydrops, undergoing comprehensive prenatal ultrasound, umbilical cord blood biochemistry, autopsy, placental pathology, and genetic testing.

Results: Prenatal ultrasound revealed fetal hydrops, skeletal anomalies, cardiac developmental abnormalities, cataracts, echogenic kidneys and bowel, oligohydramnios, choroid plexus cysts, and intrauterine growth restriction. Umbilical cord blood biochemistry demonstrated fetal anemia, coagulation disorders, and abnormal liver and kidney function. Autopsy confirmed fetal hydrops and associated anomalies. A novel compound heterozygous mutation comprising the missense variant c.754T>C (p.Ser252Pro) and a partial exonic deletion (deletion of exons 1-2) in the ALG8 gene was identified in fetus P2.

Conclusions: This study represents the first prenatal diagnosis of ALG8-CDG, comprehensively delineating the prenatal phenotypic spectrum. Prenatal ultrasound, umbilical cord blood biochemistry, and placental pathology findings aid in the assessment of prenatal manifestations, invaluable for prenatal diagnosis, genetic counseling, and potential interventions in future patients.