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. Biochemical investigations including serum N-glycan profiling, fucosylation-focused whole serum glycoprotein profiling, and serum lectin blots, all of which showed significant global hypofucosylation. Exome sequencing revealed a single likely pathogenic variant, SLC35C1 (NM_018389.4):c.503_505delTCT, p.(Phe168del), which was inherited from an unaffected mother. Whole genome sequencing with manual review of raw data did not reveal any second pathogenic variants; SLC35C1 mRNA sequencing was negative for changes in the second allele or allelic imbalance. The patient was started on L-fucose supplementation, with subsequent improvements in weight and head circumference, normalization of IgG levels, and remarkable developmental catch-up. Biochemically, there was an increase in abundance of previously decreased fucosylated glycan species in serum, especially Fuc1GlcNAc2Man3 (a glycan that is known to be enriched in neutrophils). In summary, we present here further evidence for the role of L-fucose supplementation in treating hypofucosylation disorders and suggest that IgG and fucosylated glycan species may be useful as biomarkers in this scenario, although further research is needed to validate them as such. It is likely that the early introduction of L-fucose in this patient may have led to the excellent developmental outcomes observed.

Bombay blood group is a rare blood phenotype, frequently misinterpreted as "O" blood group, and sometime causes severe hemolytic transfusion reactions. We are reporting a 4-year-old cardiac patient with congenital heart disease. During routine intraoperative evaluation, the patient was confirmed as having Bombay blood group and leukocyte adhesion deficiency type II. As this condition is extremely rare in Saudi Arabia, matched blood donors were secured from outside the country. The patient underwent bilateral peripheral artery stenosis reconstruction. Successful intraoperative management was done using one unit of matched blood transfusion, acute normovolemic hemodilution strategy, intravenous injection of antifibrinolytic agents, and regular antimicrobial surgical prophylaxis. The postoperative period was uneventful, and the patient was discharged from the hospital 1 week later. Correct and preoperative identification of Bombay phenotype, patient labeling and flagging, maintaining records for rare blood groups, and collaborations with other blood banks are necessary strategies for safe management of patients with Bombay blood group.

Congenital disorders of glycosylation (CDG) are a large family of genetic diseases resulting from defects in the synthesis of glycans and the attachment of glycans to macromolecules. The CDG known as leukocyte adhesion deficiency II (LAD II) is an autosomal, recessive disorder caused by mutations in the SLC35C1 gene, encoding a transmembrane protein of the Golgi apparatus, involved in GDP-fucose transport from the cytosol to the Golgi lumen. In this study, a cell-based model was used as a tool to characterize the molecular background of a therapy based on a fucose-supplemented diet. Such therapies have been successfully introduced in some (but not all) known cases of LAD II. In this study, the effect of external fucose was analyzed in SLC35C1 KO cell lines, expressing 11 mutated SLC35C1 proteins, previously discovered in patients with an LAD II diagnosis. For many of them, the cis-Golgi subcellular localization was affected; however, some proteins were localized properly. Additionally, although mutated SLC35C1 caused different α-1-6 core fucosylation of N-glycans, which explains previously described, more or less severe disorder symptoms, the differences practically disappeared after external fucose supplementation, with fucosylation restored to the level observed in healthy cells. This indicates that additional fucose in the diet should improve the condition of all patients. Thus, for patients diagnosed with LAD II we advocate careful analysis of particular mutations using the SLC35C1-KO cell line-based model, to predict changes in localization and fucosylation rate. We also recommend searching for additional mutations in the human genome of LAD II patients, when fucose supplementation does not influence patients' state.

Leukocyte adhesion deficiency type II (LAD II, also known as SLC35C1-congenital disorder of glycosylation) is an autosomal recessive disorder characterized by growth and cognitive impairment, peripheral neutrophilia, recurrent infections, and the Bombay blood phenotype. A subset of patients with a milder presentation has been described with short stature and developmental delay but minimal immune and hematologic features. Some patients with LAD II benefit from oral fucose therapy, though this has not been previously studied in patients with milder disease. In this study, we describe two new patients from separate families with the milder variant of LAD II and review the published literature on this rare disorder. We demonstrate improvement in speech and cognition, CD15 expression, and core fucosylation of serum glycoproteins after 27 months of oral fucose supplementation in one patient. These patients further support the stratification of this disorder into distinct subtypes, a classical severe and an attenuated variant, and provide preliminary evidence of benefit of fucose therapy in the latter group.

Individuals with the Bombay phenotype (Oh) in the ABO blood group system do not express the H, A, and B antigens but have no clinical symptoms. Bombay phenotype with clinical symptoms has been described in leukocyte adhesion deficiency type II (LAD II), a fucosylation disorder caused by mutations in SLC35C1. Only few LAD II patients have been described so far. Here we describe an additional patient, a 22-year old male, born to unrelated parents, presenting with inflammatory skin disease, periodontitis, growth, and mental retardation, admitted to the department of dentistry for treatment under general anesthesia. Pre-operative routine investigations revealed the presence of the Bombay phenotype (Oh). Genomic sequencing identified two novel triplet deletions of the SLC35C1 gene. Functional investigations confirmed the diagnosis of LAD II. Therapy with oral fucose led to the disappearance of the chronic skin infections and improvements in behavior and attention span.