NANS-CDG: Expanding clinical insights with a novel patient with novel variants.

N-acetyl-d-neuraminic acid synthase-congenital disorder of glycosylation (NANS-CDG) is a rare autosomal recessive defect in the N-acetyl-neuraminic acid biosynthesis pathway. Herein, we report the first Korean NANS-CDG patient. A 10-year-old boy was referred to our clinic because of incidental radiographic findings indicating spondyloepimetaphyseal dysplasia. The patient had microcephaly, cavum septum pellucidum, and ventriculomegaly at birth, and at 10 years, a very short stature. He had a history of idiopathic chronic immune thrombocytopenia, central adrenal insufficiency, and hypothyroidism since infancy. The first unprovoked seizure occurred at the age of 2 years, and he was subsequently admitted to the hospital frequently because of respiratory infections and intractable seizures. Exome sequencing identified unreported biallelic variants of the NANS gene. Clinical and genetic confirmation of NANS-CDG highlights its expanding phenotypic and genotypic diversity.