A case with congenital disorder of glycosylation with defective fucosylation 2 and new mutation in FUK gene

Abstract

Introduction: Congenital disorders of glycosylation (CDG) is a group of rare, hereditary, multisystem disorders, predominantly affecting nervous system. There are N- and O- types of glycosylation. Fucosylation, a form of N-glycosylation, involves many enzymes. Until today, type 1 and type 2 fucosylation defects were identified, having pathogenic variants in genes encoding α-1,6-fucosyltransferase and fucokinase enzymes, respectively. In this article, a patient with type 2 fucosylation defect will be presented, with hypotonia, developmental delay and blindness and a pathogenic variant that was previously described in two patients.

Method: Whole exome sequencing (WES) was performed, since the patient had no time to implement diagnostic algorithm for hypotonia etiology.

Results: WES revealed a new pathogenic variant of homozygous c.993_1011del (p.Glu335Hisfs*55) frameshift variant of the FUK gene NM_145059 transcript. She had milder clinical manifestation than reported two patients.

Conclusion: Congenital Defect of Glycosylation should be considered when the clinical findings cannot be explained by other known diseases, particularly in patients with multisystemic, predominantly neurological involvement.

Keywords: Congenital defect of glycosylation; Developmental delay; Hypotonia; Type2 fucosylation defect.