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- Congenital disorders of glycosylationPublication . Mendes, Ana Raquel; Quelhas, D; Correia, Joana; Paiva Coelho, Margarida; Bandeira, Anabela; Martins, EsmeraldaCongenital disorders of glycosylation are a highly variable, rapidly expanding family of genetic diseases that result from defects in the synthesis of glycans. The vast majority of these monogenic diseases are inherited in an autosomal recessive way, but some types follow an autosomal dominant or X-linked inheritance. The present work aimed to review the state of the art of congenital disorders of glycosylation, including available therapeutic options, and present a simplified diagnostic approach to this group of diseases. Congenital disorders of glycosylation can be classified into four categories: N-linked glycosylation defects, O-linked glycosylation defects, combined glycosylation defects, and glycosphingolipid and glycosylphosphatidylinositol anchor synthesis defects. The phenotype may range from mild to severe, depending on disease severity. Clinical features include dysmorphic features, neurologic, dermatologic, cardiac, endocrine, immunologic, hematologic, gastrointestinal and liver involvement, and skeletal muscle abnormalities. As there is no universal or pathognomonic sign or symptom and no sensitive diagnostic test, it is of foremost importance to keep a high index of suspicion of these diseases. When a congenital disorder of glycosylation is suspected, the first step in screening is to perform serum transferrin isoelectric focusing. Molecular genetic testing is the most specific diagnostic test. Treatment is usually symptomatic, with specific treatment only available for some of these disorders. Since congenital defects of glycosylation may affect any organ at any age and have variable clinical presentation, they should be considered in the differential diagnosis of any patient with multiorgan involvement.
- Genotype-Phenotype Correlations in PMM2-CDGPublication . Vaes, Laurien; Rymen, Daisy; Cassiman, David; Ligezka, Anna; Vanhoutvin, Nele; Quelhas, D; Morava, Eva; Witters, PeterPMM2-CDG is a rare disease, causing hypoglycosylation of multiple proteins, hence preventing full functionality. So far, no direct genotype-phenotype correlations have been identified. We carried out a retrospective cohort study on 26 PMM2-CDG patients. We collected the identified genotype, as well as continuous variables indicating the disease severity (based on Nijmegen Pediatric CDG Rating Score or NPCRS) and dichotomous variables reflecting the patients' phenotype. The phenotypic effects of patients' genotype were studied using non-parametric and Chi-Square tests. Seventeen different pathogenic variants have been studied. Variants with zero enzyme activity had no significant impact on the Nijmegen score. Pathogenic variants involving the stabilization/folding domain have a significantly lower total NPCRS (p = 0.017): presence of the p.Cys241Ser mutation had a significantly lower subscore 1,3 and NPCRS (p = 0.04) and thus result in a less severe phenotype. On the other hand, variants involving the dimerization domain, p.Pro113Leu and p.Phe119Leu, resulted in a significantly higher NPCRS score (p = 0.002), which indicates a worse clinical course. These concepts give a better insight in the phenotypic prognosis of PMM2-CDG, according to their molecular base.