L-fucose supplementation in a patient with global hypofucosylation and a mono-allelic variant in SLC35C1: Clinical improvement and assessment of biomarkers

Fucosylation disorders are rare types of congenital disorders of glycosylation (CDG), the most common being SLC35C1-CDG, which is classically described as a leukocyte adhesion deficiency (hence the previous name of “leukocyte adhesion deficiency type II”) with dysmorphic features, short stature, and moderate-to-severe developmental and intellectual disabilities. In more recent years, several cases have been described of individuals with bi-allelic SLC35C1 variants and biochemical proof of hypofucosylation who had short stature, dysmorphic features, and intellectual disability, but no hematological abnormalities. In this article, we report a patient with growth faltering, neuroirritability, nystagmus, developmental delays, microcephaly, dysmorphic features, and hypogammaglobulinemia G.