MOGS-congenital disorder of glycosylation (MOGS-CDG) is rare genetic disorder caused by biallelic variants in MOGSgene, which codes for mannosyl-oligosaccharide glucosidase. MOGS-CDG is extremely rare with around 30 patients described up to date (2025). It is inherited in autosomal recessive manner. MOGS-CDG is caused by deficiency of MOGS enzyme, which is crucial in the correct processing of the N-glycans in the endoplasmic reticulum (ER). MOGS deficiency therefore leads to glycosylation abnormalities, resulting in a CDG type II pattern. Based on this classification, MOGS-CDG has been previously known as CDG-type IIb.
MOGS-CDG patients have variable clinical features including early onset developmental delay and hypotonia, epilepsy, brain MRI changes such as thin corpus callosum, dystonia, hypogammaglobulinemia, dysmorphic features, liver, skeletal and cardiac involvement. However, patient with isolated neurological phenotype have also been reported. Life expectancy is variable, from death in early infancy to survival into early adulthood. The oldest reported patient was 19.
MOGS-CDG can be diagnosed by biochemical methods such as measuring tetrasaccharide Glucose3-Mannnose (Glc3Man) in urine or abnormal glycosylation by transferrin isoelectric focusing (TIEF) or other comparable methods. However, the definitive diagnosis is most often made on the basis of genetic testing such as whole exome sequencing (WES).
To date, there are no curative treatments for MOGS-CDG.
MOGS