Classification Historically,<unk> s are classified as Types I and II <unk> -I and<unk> -II), depending on the nature and location of the biochemical defect in the metabolic pathway relative to the action of oligosaccharyltransferase. The most commonly used screening method for<unk> , analysis of transferrin<unk>  status by isoelectric focusing, ESI-MS, or other techniques, distinguish between these subtypes in so called Type I and Type II patterns. Currently, twenty-two<unk>  Type-I and fourteen Type-II subtypes of<unk>  have been described. Since 2009, most researchers use a different nomenclature based on the gene defect (e.g.<unk> -Ia = PMM2-CDG,<unk> -Ib = PMI-CDG,<unk> -Ic = ALG6-CDG etc.). The reason for the new nomenclature was the fact that proteins not directly involved in glycan synthesis (such as members of the COG-family and vesicular H+-ATPase) were found to be causing the<unk>  defect in some<unk>  patients. Also, defects disturbing other<unk>  pathways than the N-linked one are included in this classification. Examples are the α-dystroglycanopathies (e.g. POMT1/POMT2-CDG (Walker-Warburg syndrome and Muscle-Eye-Brain syndrome)) with deficiencies in O-mannosylation of proteins; O-xylosylglycan synthesis defects (EXT1/EXT2-CDG (hereditary multiple exostoses) and B4GALT7-CDG (Ehlers-Danlos syndrome, progeroid variant)); O-fucosylglycan synthesis (B3GALTL-CDG (Peter's plus syndrome) and LFNG-CDG (spondylocostal dysostosis III)). Type I * Type I<unk> s involve disrupted synthesis of the lipid-linked oligosaccharide precursor (LLO) or its transfer to the protein. Types include: Type OMIM Gene Locus Ia (PMM2-CDG) PMM2 16p13.3-p13.2 Ib (MPI-CDG) MPI 15q22-qter Ic (ALG6-CDG) ALG6 1p22.3 Id (ALG3-CDG) ALG3 3q27 Ie (DPM1-CDG) DPM1 20q13.13 If (MPDU1-CDG) MPDU1 17p13.1-p12 Ig (ALG12-CDG) ALG12 22q13.33 Ih (ALG8-CDG) ALG8 11pter-p15.5 Ii (ALG2-CDG) ALG2 9q22 Ij (DPAGT1-CDG) DPAGT1 11q23.3 Ik (ALG1-CDG) ALG1 16p13.3 1L (ALG9-CDG) ALG9 11q23 Im (DOLK-CDG) DOLK 9q34.11 In (RFT1-CDG) RFT1 3p21.1 Io (DPM3-CDG) DPM3 1q12-q21 Ip (ALG11-CDG) ALG11 13q14.3 Iq (SRD5A3-CDG) SRD5A3 4q12 Ir (DDOST-CDG) DDOST 1p36.12 DPM2-CDG DPM2 9q34.13 TUSC3-CDG TUSC3 8p22 MAGT1-CDG MAGT1 X21.1 DHDDS-CDG DHDDS 1p36.11 I/IIx n/a n/a Type II * Type II<unk> s involve malfunctioning trimming/processing of the protein-bound oligosaccharide chain. Types include: Type OMIM Gene Locus IIa (MGAT2-CDG) MGAT2 14q21 IIb (GCS1-CDG) GCS1 2p13-p12 IIc (SLC335C1-CDG; Leukocyte adhesion deficiency II)) SLC35C1 11p11.2 IId (B4GALT1-CDG) B4GALT1 9p13 IIe (COG7-CDG) COG7 16p IIf (SLC35A1-CDG) SLC35A1 6q15 IIg (COG1-CDG) COG1 17q25.1 IIh (COG8-CDG) COG8 16q22.1 IIi (COG5-CDG) COG5 7q31 IIj (COG4-CDG) COG4 16q22.1 IIL (COG6-CDG) COG6 13q14.11 IIT <unk> 2T) GALNT2 ATP6V0A2-CDG (autosomal recessive cutis laxa type 2a (ARCL-2A)) ATP6V0A2 12q24.31 MAN1B1-CDG (Mental retardation, autosomal recessive 15) MAN1B1 9q34.3 ST3GAL3-CDG (Mental retardation, autosomal recessive 12) ST3GAL3 1p34.1<unk> s of O-mannosylation *<unk> s with deficient α-dystroglycan O-mannosylation. Mutations in several genes have been associated with the traditional clinical syndromes, termed muscular dystrophy-dystroglycanopathies (MDDG). A new nomenclature based on clinical severity and genetic cause was recently proposed by OMIM. The severity classifications are A (severe), B (intermediate), and C (mild). The subtypes are numbered one to six according to the genetic cause, in the following order: (1) POMT1, (2) POMT2, (3) POMGNT1, (4) FKTN, (5) FKRP, and (6) LARGE. Most common severe types include: Name OMIM Gene Locus POMT1-CDG (MDDGA1;Walker-Warburg syndrome) POMT1 9q34.13 POMT2-CDG (MDDGA2;Walker-Warburg syndrome) POMT2 14q24.3 POMGNT1-CDG (MDDGA3; muscle-eye-brain) POMGNT1 1p34.1 FKTN-CDG (MDDGA4; Fukuyama<unk>  muscular dystrophy) FKTN 9q31.2 FKRP-CDG (MDDGB5; MDC1C) FKRP 19q13.32 LARGE-CDG (MDDGB6; MDC1D) LARGE 22q12.3
Congenital disorder of glycosylation
GM2 gangliosidoses
GM1 gangliosidoses
Mucopolysaccharidosis
Inborn errors of carbohydrate metabolism
Sphingolipidoses
Lysinuric protein intolerance
Infantile free sialic acid storage disease