What is ALG9-CDG?

A form of congenital disorders of N-linked glycosylation characterized by progressive microcephaly, hypotonia, developmental delay, drug-resistant infantile epilepsy, and hepatomegaly. Additional features that may be observed include failure to thrive, pericardial effusion, renal cysts, skeletal dysplasia, facial dysmorphism (frontal bossing, hypertelorism, depressed nasal bridge, low-seated ears, large mouth) and hydrops fetalis. The disease is caused by loss-of-function mutations in the gene ALG9 (11q23).

Other condition names

  • CDG syndrome type IL
  • CDG-IL
  • CDG1L
  • Carbohydrate deficient glycoprotein syndrome type IL
  • Congenital disorder of glycosylation type 1L
  • Mannosyltransferase 7-9 deficiency

Inheritance type

Autosomal recessive


  • Worldwide: <1 in 1,000 000

Age of Onset

  • Infancy
  • Neonatal
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