disorders of glycosylation or Carbohydrate-Deficient Glycoprotein Syndrome
disorders of glycosylation or carbohydrate-deficient glycoprotein syndrome
presents in the neonatal period with inverted nipples,
hypotonia, abnormal distribution of fat (Figure 123.1 A-C) and pontocerebellar
hypoplasia. Trunk hypotonia may be more pronounced than limb hypotonia.
The abnormal accumulation of fat produces a puffy and uneven skin (Figure
123.1 B), and increased subcutaneous tissue around the external genitalia
and around the buttocks (Figure 123.1 C). The combination of slender legs
(limb waisting due to hypoactivity) and prominent deposition of fat in
the buttocks produces a characteristic appearance (Figure 123.1 C). The
diagnosis of carbohydrate-deficient glycoprotein syndrome is established
by the detection in serum or CSF of abnormal transferrin isoforms. The
tests for this purpose are: (1) carbohydrate-deficient transferin assay,
or (2) isoelectric focusing of serum transferrin. The disease is due to
hypoglycosylation of glycoproteins. There are several types of congenital
disorders of glycosylation. Type I is due to a deficiency of phosphomannomutase.
Congenital disorder of glycosylation type I is an autosomic recessive
disease. The abnormalities is probably in chromosomes 16p. The dysfunctional
cellular organelle is probably the endoplasmatic reticulum.
Figure 123.1— Congenital disorders of
glycosylation or carbohydrate-deficient glycoprotein syndrome.
[A] accumulation of fat between the ear cartilage and skin; [B]
puffy and uneven skin of the arm and inverted nipple; [C]
prominent deposition of fat in the buttocks and waisted legs.
with congenital pontocerebellar hypoplasia may be hypotonic at birth.
Congenital pontocerebellar hypoplasia may have an autosomal dominant or
recessive inheritance. Magnetic resonance imaging of the brain is diagnostic
(Figure 123.2). Pontocerebellar hypoplasia may occur in association with
spinal muscular atrophy.
pontocerebellar hypoplasia. [A] T1-weighted sagittal
image demonstrates brainstem atrophy and cerebellar hypoplasia. [B] T1-weighted
axial image demonstrates an empty posterior fossa.