Table 3a.

Metabolic Disorders to Consider in the Differential Diagnosis of PMM2-CDG in Infants Who Have Not Yet Had an MRI

GenesDiffDx DisorderOverlapping Clinical FeaturesDistinguishing Features
>175 genesOther CDGs 1 & CDDGs (See CDG-N-Linked & Multiple Pathway Overview & NGLY1-CDDG.)
  • IUGR
  • DD/ID
  • Neurologic dysfunction
  • Liver disease
  • Can have abnormal transferrin glycoform analysis
  • Can be indistinguishable
  • PMM2 enzyme activity is abnormal only in PMM2-CDG.
>300 genes

Mitochondrial disorders

  • Multisystem involvement
  • Pigmentary retinopathy
  • Movement disorder
Persons w/PMM2-CDG:
  • Do not typically have episodes of metabolic decompensation or clinical presentations assoc w/classic mt disorder phenotypes;
  • Do not typically have significantly ↑ acidemia if not assoc w/hypoperfusion;
  • Have abnormal transferrin glycoform analysis & deficient PMM2 activity.
>20 genesPeroxisomal biogenesis defects (See Zellweger Spectrum Disorder.)
  • Multisystem involvement
  • DD/ID
  • Neurologic dysfunction
  • Liver disease
Persons w/PMM2-CDG do not have abnormal very long chain fatty acids.
>20 genesUrea cycle disorders / organic acidemias (See Propionic Acidemia, Glutaric Acidemia Type 1, Isolated Methylmalonic Acidemia, & Disorders of Intracellular Cobalamin Metabolism.)
  • Hypotonia
  • Growth deficiency
  • Feeding intolerance
  • DD/ID
  • Spasticity
Persons w/PMM2-CDG:
  • Do not typically have episodes of metabolic decompensation;
  • Do not have hyperammonemia;
  • Have abnormal transferrin glycoform analysis & deficient PMM2 activity.

CDDG = congenital disorder of deglycosylation; CDG = congenital disorder of glycosylation; CDG-N-linked = congenital disorders of N-linked glycosylation; DD = developmental delay; DiffDx = differential diagnosis; ID = intellectual disability; IUGR = intrauterine growth restriction; mt = mitochondrial; NGLY1-CDDG = NGLY1-related congenital disorder of deglycosylation

1.

See OMIM Phenotypic Series: Congenital Disorders of Glycosylation, Type I and Congenital Disorders of Glycosylation, Type II to view genes associated with these phenotypes.

From: PMM2-CDG

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