EP06.05: Prenatal ultrasound findings of congenital disorders of glycosylation type Id: a case report

Congenital disorders of glycosylation (CDG) are a group of rare autosomal recessive disorders characterised by hypoglycosylation of glycoproteins and glycolipids. CDG-Id type is characterised by alpha-1,3-mannosyltransferase deficiency caused by a variant in the ALG3 gene and is one of the rare types of CDG. The ALG3 gene variant results in the CDG-Id phenotype, with only 43 cases reported to date. The CDG-Id phenotype usually involves multiple organs and has diverse clinical presentations. The pregnant woman was 32 years old, G7P1, whose fifth singleton pregnancy had fetal malformations suggested by ultrasound in other hospital, and after termination of pregnancy, she came to our hospital for genetic testing with the result of ALG3 gene variant (NM_005787:c.67C>T(p.Gln23*), Heterozygote, Paternal; NM_005787:c.1188G>A(p.Trp396*), Heterozygote, Maternal), which can lead to CDG-Id. The sixth pregnancy had no abnormalities on prenatal ultrasound diagnosis or genetic testing; prenatal genetic testing suggested that the fetus was of wild type; and a baby girl was delivered at term with good health. In this seventh singleton pregnancy at 21 weeks of gestation, prenatal ultrasound at our hospital demonstrated multiple fetal malformations, with micrognathia, cerebellar vermis absence, cystic occupancy of the posterior cranial fossa, all long bones of the limbs are short, scoliosis and stiffness of the finger joints as the main manifestations. The pregnancy was then terminated at another hospital, and subsequent genetic testing results confirmed that it was also ALG3 gene variant. Prenatal ultrasound manifestations of CDG-Id type have not been reported in the literature. When we find abnormalities such as micrognathia, cerebellar vermis absence, fetal growth restriction, scoliosis, polyarticular contractures, etc., we can advise pregnant women and their families to undergo genetic testing and genetic counselling to provide more valuable information for clinical management.