P090: SC4MOL deficiency: 11th reported patient with updates in treatment outcomes and review of reported cases

Case Presentation: Patient 1 is a 19-month-old male diagnosed prenatally on amniocentesis with compound heterozygous variants in MOGS (c.1675c>T, p.S559P and c.311A>C, p.Y104S) of biparental inheritance after GS in one of her previous affected children revealed the same variants.He is G-tube and ventilator dependent, has severe hypotonia, global developmental delay, epilepsy, anemia, without frequent infections, and has a Nijmegen pediatric CDG rating scale score of 31 (severe).Patient 2 is the 4-month-old female sibling of Patient 1 and was also diagnosed prenatally with the same compound heterozygous variants in MOGS as Patient 1.She is G-tube and ventilator dependent, has epilepsy, hypothyroidism, global developmental delay, hypotonia, pulmonary valve thickening, adrenal insufficiency, dysmorphic facies, has had multiple, severe bacterial infections, and a Nijmegen pediatric CDG rating scale score of 31 (severe).Diagnostic Workup: Diagnosis in MOGS-CDG is complicated by the fact that CDT testing is rarely positive in these patients, however, urine oligosaccharide testing is diagnostic in 100% of patients.In the case of our two patients, since familial pathogenic variants were already known, molecular testing was used first line for prenatal diagnosis.Both patients also had quantitative immunoglobulins sent which are non-diagnostic for both patients since they were drawn before 6 months of age.Patient 1 had urine oligosaccharides sent which revealed a profile consistent with his molecular diagnosis.