Syndrome with characteristics of severe psychomotor retardation, failure to thrive and intolerance to wheat and dairy products. So far, only two cases have been described. The disease is caused by mutations in the COG8 gene, which encodes a subunit of the COG complex. This complex is involved vesicle transport in the Golgi apparatus.

Congenital disorders of glycosylation (CDGs) are a genetically heterogeneous group of autosomal recessive disorders caused by enzymatic defects in the synthesis and processing of asparagine (N)-linked glycans or oligosaccharides on glycoproteins. These glycoconjugates play critical roles in metabolism, cell recognition and adhesion, cell migration, protease resistance, host defense, and antigenicity, among others. CDGs are divided into 2 main groups: type I CDGs (see, e.g., CDG1A, 212065) comprise defects in the assembly of the dolichol lipid-linked oligosaccharide (LLO) chain and its transfer to the nascent protein, whereas type II CDGs refer to defects in the trimming and processing of the protein-bound glycans either late in the endoplasmic reticulum or the Golgi compartments. The biochemical changes of CDGs are most readily observed in serum transferrin (TF; 190000), and the diagnosis is usually made by isoelectric focusing of this glycoprotein (reviews by Marquardt and Denecke, 2003; Grunewald et al., 2002). Genetic Heterogeneity of Congenital Disorder of Glycosylation Type II Multiple forms of CDG type II have been identified; see CDG2B (606056) through CDG2Z (620201), and CDG2AA (620454) to CDG2BB (620546).

CDG IIe is caused by a mutation that impairs the integrity of the conserved oligomeric Golgi (COG) complex and alters Golgi trafficking, resulting in the disruption of multiple glycosylation pathways. For a general discussion of CDGs, see CDG1A (212065).

An extremely rare form of carbohydrate deficient glycoprotein syndrome with, in the few cases reported to date, variable signs including microcephaly, growth retardation, psychomotor retardation and facial dysmorphism.

COG5-congenital disorder of glycosylation (COG5-CDG, formerly known as congenital disorder of glycosylation type IIi) is an inherited condition that causes neurological problems and other abnormalities. The pattern and severity of this disorder's signs and symptoms vary among affected individuals.\n\nIndividuals with COG5-CDG typically develop signs and symptoms of the condition during infancy. These individuals often have weak muscle tone (hypotonia) and delayed development. Other neurological features include moderate to severe intellectual disability, poor coordination, and difficulty walking. Some affected individuals never learn to speak. Other features of COG5-CDG include short stature, an unusually small head size (microcephaly), and distinctive facial features, which can include ears that are set low and rotated backward, a short neck with a low hairline in the back, and a prominent nose. Less commonly, affected individuals can have hearing loss caused by changes in the inner ear (sensorineural hearing loss), vision impairment, damage to the nerves that control bladder function (a condition called neurogenic bladder), liver disease, and joint deformities (contractures).

CDG2L is an autosomal recessive multisystem disorder apparent from birth or early infancy. It is characterized by poor growth, gastrointestinal and liver abnormalities, delayed psychomotor development, hypotonia, recurrent infections, hematologic abnormalities, increased bleeding tendency, and hyperhidrosis or hyperkeratosis. More variable features include nonspecific dysmorphic facial features and cardiac septal defects. The disorder often results in death in infancy or the first years of life (summary by Rymen et al., 2015). For a general discussion of CDGs, see CDG1A (212065) and CDG2A (212066).

Congenital disorder of glycosylation type IIp (CDG2P) is an autosomal recessive metabolic disorder characterized by mild liver dysfunction, which may be found incidentally during adolescence. Laboratory abnormalities include elevated liver enzymes and alkaline phosphatase, coagulation factor deficiencies, hypercholesterolemia, and low ceruloplasmin. Serum isoelectric focusing of proteins shows a combined defect of N- and O-glycosylation, suggestive of a Golgi defect (summary by Jansen et al., 2016). For an overview of congenital disorders of glycosylation, see CDG1A (212065) and CDG2A (212066).

An extremely rare form of carbohydrate deficient glycoprotein syndrome with, in the single reported case to date, seizures, some dysmorphic features, axial hypotonia, slight peripheral hypertonia and hyperreflexia.

Immunodeficiency-47 (IMD47) is an X-linked recessive complex syndrome characterized by liver dysfunction, recurrent bacterial infections, hypogammaglobulinemia, and defective glycosylation of serum proteins. Some patients also have neurologic abnormalities (summary by Jansen et al., 2016).

Autosomal recessive cutis laxa type IIC (ARCL2C) is characterized by generalized skin wrinkling with sparse subcutaneous fat and dysmorphic progeroid facial features. Most patients also exhibit severe hypotonia as well as cardiovascular involvement (summary by Van Damme et al., 2017). For a general phenotypic description and a discussion of genetic heterogeneity of autosomal recessive cutis laxa, see ARCL1A (219100).

Congenital disorder of glycosylation type 2R (CDG2R) is an X-linked recessive disorder characterized by infantile onset of liver failure, recurrent infections due to hypogammaglobulinemia, and cutis laxa. Some patients may also have mild intellectual impairment and dysmorphic features. Laboratory studies showed defective glycosylation of serum transferrin in a type 2 pattern (summary by Rujano et al., 2017). For an overview of congenital disorders of glycosylation, see CDG1A (212065) and CDG2A (212066).

Congenital disorder of glycosylation type IIw (CDG2W) is an autosomal dominant metabolic disorder characterized by liver dysfunction, coagulation deficiencies, and profound abnormalities in N-glycosylation of serum specific proteins. All reported patients carry the same mutation (602671.0017) (summary by Ng et al., 2021). For an overview of congenital disorders of glycosylation, see CDG1A (212065) and CDG2A (212066).

Congenital disorder of glycosylation type IIy (CDG2Y) is an autosomal recessive multisystemic congenital disorder characterized by poor overall growth and global developmental delay with impaired intellectual development. Other features may include hypotonia, seizures, brain imaging abnormalities, dysmorphic features, and various skeletal defects. Laboratory studies show a subtle type II glycosylation defect of serum transferrin (Tambe et al., 2020). For a general discussion of CDGs, see CDG1A (212065).

Congenital disorder of glycosylation type IIz (CDG2Z) is an autosomal recessive disorder characterized by poor overall growth, severe global developmental delay, seizures, contractures, hypotonia, spasticity, and brain imaging abnormalities. Serum transferrin shows a type 2 pattern of glycosylation abnormalities with a combined N- and O-glycosylation defect (Wilson et al., 2022). For a general discussion of CDGs, see CDG1A (212065).