GTR Home > Conditions/Phenotypes > METHYLCOBALAMIN DEFICIENCY, cblG TYPE

Disease characteristics

Excerpted from the GeneReview: Disorders of Intracellular Cobalamin Metabolism
The clinical manifestations of disorders of intracellular cobalamin metabolism can be highly variable even within a single complementation group. The prototype and best understood is cblC; it is also the most common of these disorders. The age of initial presentation of cblC spans a wide range, including: Newborns, who can have intrauterine growth retardation (IUGR) and microcephaly; Infants, who can have poor feeding, failure to thrive, pallor, and neurologic signs, and occasionally hemolytic uremic syndrome (HUS) and/or seizures including infantile spasms; Toddlers, who can have failure to thrive, poor head growth, cytopenias (including megaloblastic anemia), global developmental delay, encephalopathy, and neurologic signs such as hypotonia and seizures; and Adolescents and adults, who can have neuropsychiatric symptoms, progressive cognitive decline, and/or subacute combined degeneration of the spinal cord.

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Associated genes

Clinical features

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  • Poor coordination
  • Gait disturbance
  • Intellectual disability
  • Hypomethioninemia
  • Seizure
  • Nystagmus
  • Failure to thrive
  • Feeding difficulties in infancy
  • Blindness
  • Global developmental delay
  • Megaloblastic anemia
  • Cerebral atrophy
  • Homocystinuria
  • Hyperhomocystinemia
  • Decreased methylcobalamin
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