This is a mechanism module, not a specific disease. Disorder entries reference individual nodes via conforms_to (e.g., "congenital_disorder_of_glycosylation#Protein Hypoglycosylation"). The single best key conformance target is the central "Protein Hypoglycosylation" node — the one event every CDG shares regardless of arm, matching the machine-checkable GO:0006487 / GO:0006491 criterion already used by the Congenital_Disorders_of_Glycosylation grouping. A type I conformer routes through the "ER Lipid-Linked Oligosaccharide Assembly Defect" trigger; a type II conformer routes through the "Golgi N-Glycan Processing and Trafficking Defect" trigger; both then conform to the shared "Protein Hypoglycosylation" hub. Conforming nodes should substitute the disorder-specific lesion (the deficient ER glycosyltransferase or dolichol-donor-utilization factor for type I; the deficient Golgi processing enzyme or COG-trafficking subunit for type II). The specificity is carried by the mechanism (hypoglycosylation), not by the diffuse terminal phenotype; disorder-private downstream biology (alpha-dystroglycan O-mannosylation in MPDU1, hyposialylation in the COG disorders) belongs on the individual disorder entries. Modules bind GO and CL terms only and do not use CHEBI or gene bindings.
ER Lipid-Linked Oligosaccharide Assembly Defect
trigger
In the type I CDG, one of the enzymes (or dolichol-donor-utilization factors) that build the lipid-linked oligosaccharide precursor on the cytosolic and luminal faces of the endoplasmic reticulum is deficient. The dolichol-linked oligosaccharide is assembled incompletely, so a truncated precursor accumulates and truncated/incomplete oligosaccharides are transferred to nascent protein instead of the full mature glycan.
Downstream
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Protein Hypoglycosylation
Golgi N-Glycan Processing and Trafficking Defect
trigger
In the type II CDG, the oligosaccharide precursor is transferred to protein normally, but its subsequent maturation in the Golgi is defective — either because a Golgi processing enzyme is deficient (e.g. MGAT2, which encodes N-acetylglucosaminyltransferase II, the branching enzyme that converts oligomannose to complex N-glycans) or because trafficking of the Golgi glycosylation machinery is disrupted (e.g. the conserved oligomeric Golgi (COG) complex disorders, which mislocalize Golgi glycosyltransferases and disrupt multiple glycosylation pathways).
Downstream
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Protein Hypoglycosylation
Protein Hypoglycosylation
central effector
Both arms converge here: many secreted and membrane client glycoproteins carry absent, truncated, or otherwise abnormal glycans. In the type I disorders this is detected as the classic cathodal shift of serum transferrin (CDG type 1 isoelectric-focusing pattern); in the COG and other type II disorders it manifests as combined deficient N- and O-glycosylation. Because glycosylation modifies a very large fraction of the proteome, hypoglycosylation degrades the folding, stability, trafficking, and function of many unrelated proteins simultaneously — the shared central lesion of the disease family.
Downstream
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Multisystem Glycoprotein Dysfunction
Multisystem Glycoprotein Dysfunction
consequence
Because so many glycoproteins are simultaneously affected, the downstream disease is characteristically multisystem: developmental delay/intellectual disability, hypotonia, and other neurologic features; hepatic dysfunction; coagulation abnormalities; immune dysfunction; dysmorphism; and, in some subtypes, skeletal or renal involvement. The precise organ pattern varies by subtype and by which client glycoproteins are most rate-limiting, but the multisystem outflow is the shared consequence of proteome-wide hypoglycosylation.