Key words congenital disorder of glycosylation, MOGS, whole exome sequencing. Congenital disorders of glycosylation (CDGs) are caused by deficient protein and lipid glycosylation. 1 Most CDGs are multisystem disorders. Mannosyl-oligosaccharide glucosidase congenital disorder of glycosylation (MOGS-CDG) is caused by recessive mutations in the mannosyl-oligosaccharide glucosidase I gene. Only six patients (from four families) have a d b c Fig. 1 (a) Clinical picture of the patient. (b) Echocardiogram of our patient revealed marked decrease in cardiac function. (c) Brain MRI scan, sagittal T1-weighted sequence displaying partial agenesis of the corpus callosum. (arrow) (d) Electropherogram shows novel compound heterozygous mutations in MOGS. Patient had compound heterozygous mutations: c.1483C>T nonsense mutation from the father and c.2255G>A missense mutation from the mother. (red arrows)