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Synonym(s) CDG syndrome type Ib
Carbohydrate deficient glycoprotein syndrome type Ib
Congenital disorder of glycosylation type 1b
Congenital disorder of glycosylation type Ib
Phosphomannose isomerase deficiency
Prevalence <1 / 1 000 000
Inheritance Autosomal recessive
Age of onset Infancy
  • E77.8
MeSH -
MedDRA -


The CDG (Congenital Disorders of Glycosylation) syndromes are a group of autosomal recessive disorders affecting glycoprotein synthesis. CDG syndrome type Ib is characterised by hepatic-intestinal manifestations (diarrhoea, vomiting, and hepatomegaly associated with hepatic fibrosis).

It has been described in 20 children.

The hepatic fibrosis may evolve towards cirrhosis and hepatic insufficiency, which is sometimes fatal. The clinical manifestations are not present at birth but appear during the first three months of life. Additional manifestations (failure to thrive, oedema, febrile episodes, thrombosis, hypoglycaemia and facial dysmorphism) were present in some cases. CDG syndrome type Ib can be differentiated from other types of CDG syndrome by the absence of neurological disease.

The syndrome is caused by mutations in the MPI gene (localised to the q22-qter region of chromosome 15) leading to a deficiency of the cytoplasmic enzyme phosphomannose isomerase.

CDG syndrome can be successfully treated by oral administration of mannose.

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Guidance for genetic testing
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Clinical genetics review
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