GTR Home > Conditions/Phenotypes > Carbohydrate-deficient glycoprotein syndrome type I

Disease characteristics

Excerpted from the GeneReview: PMM2-CDG (CDG-Ia)
PMM2-CDG (CDG-Ia) (previously known as congenital disorder of glycosylation type 1a), the most common of a group of disorders of abnormal glycosylation of N-linked oligosaccharides, is divided into three stages: infantile multisystem, late-infantile and childhood ataxia-intellectual disability, and adult stable disability. The three stages notwithstanding, clinical presentation and course are highly variable, ranging from infants who die in the first year of life to mildly involved adults. Clinical presentations tend to be similar in siblings. In the infantile multisystem stage, infants show axial hypotonia, hyporeflexia, esotropia, and developmental delay; feeding problems, vomiting, and diarrhea with failure to thrive; and impaired growth. Subcutaneous fat may be excessive over the buttocks and suprapubic region. Two distinct clinical presentations are observed: (1) a non-fatal neurologic form with strabismus, psychomotor retardation, and cerebellar hypoplasia in infancy followed by neuropathy and retinitis pigmentosa in the first or second decade and (2) a neurologic-multivisceral form with approximately 20% mortality in the first year of life. The late-infantile and childhood ataxia-intellectual disability stage, with onset between age three and ten years, is characterized by hypotonia, ataxia, severely delayed language and motor development, inability to walk, and IQ of 40 to 70; other findings include stroke-like episodes or transient unilateral loss of function, retinitis pigmentosa, joint contractures, and skeletal deformities. In the adult stable disability stage, intellectual ability is stable; peripheral neuropathy is variable, thoracic and spinal deformities progress, and premature aging is observed; females lack secondary sexual development and males may exhibit decreased testicular volume. Hyperglycemia-induced growth hormone release, hyperprolactinemia, insulin resistance, and coagulopathy may occur. An increased risk of deep venous thrombosis is present.

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Associated genes

Clinical features

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  • Proteinuria
  • Muscle weakness
  • Prolonged prothrombin time
  • Hyporeflexia
  • Hypoalbuminemia
  • Prolonged partial thromboplastin time
  • Abnormality of the amniotic fluid
  • IgA deficiency
  • Prominent forehead
  • Kyphosis
  • Microcephaly
  • IgG deficiency
  • Nonimmune hydrops fetalis
  • Stroke-like episodes
  • Olivopontocerebellar hypoplasia
  • Proximal tubulopathy
  • Abnormal subcutaneous fat tissue distribution
  • Macrotia
  • Seizure
  • Diarrhea
  • Nystagmus
  • Osteopenia
  • Renal cyst
  • Failure to thrive
  • Feeding difficulties in infancy
  • Vomiting
  • Hypothyroidism
  • Nephrotic syndrome
  • Thin upper lip vermilion
  • Retinitis pigmentosa
  • Esotropia
  • Hypergonadotropic hypogonadism
  • Ataxia
  • Muscular hypotonia
  • Global developmental delay
  • Polyneuropathy
  • Flexion contracture
  • Hepatic fibrosis
  • Hepatic steatosis
  • Primary ovarian failure
  • Cardiomyopathy
  • Pericardial effusion
  • Thrombocytosis
  • Reduced factor XI activity
  • Reduced antithrombin III activity
  • Hepatomegaly
  • Elevated hepatic transaminases
  • Hypocholesterolemia
  • Inverted nipples
  • Type I transferrin isoform profile
  • Depressed nasal bridge
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