Congenital disorders of glycosylation (CDG) are a group of heterogeneous disorders caused by abnormal lipid or protein glycosylation. Variants in the FCSK gene have been reported to cause CDG. Defective FCSK-induced CDG (FCSK-CDG) has only been reported previously in three unrelated children. […] In this study, we genetically and clinically examined a 3-year-old proband with resolved infantile spasms and normal development. WES revealed a rare biallelic missense variant (c.3013G>C; p.Val1005Leu) in FCSK.