Neuro-Ophthalmic Presentation of Steroid 5a-Reductase Type 3 Congenital Disorder of Glycosylation: A Case of Monozygotic Twins

We report a very rare autosomal recessive metabolic disorder in monozygotic twin sisters caused by the steroid 5a-reductase type 3 (SRD5A3) gene defect, a subtype of congenital disorder of glycosylation (CDG). SRD5A3 activity is required for N-glycosylation of proteins. This step is important for the protein to gain its function. The condition is characterized by severe neurodevelopmental delay, cerebellar atrophy or hypoplasia, ocular abnormalities, and ichthyotic skin changes. We describe 20-month-old female monozygotic twins born to non-consanguineous South Asian parents.