Glossary in Congenital Malformations
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#Jacobsen
syndrome (deletion 11q syndrome):
·
Genetics: There
is deletion of chromosome 11q23 to qter in most cases and the region related to
the clinical phenotype appears to be located on 11q24.1. Three quarter of the
patients are female. Deletion of 11q may arise de novo or from inheriting a
derived chromosome from a parent carrying a balanced translocation.
·
Clinical
features: Intrauterine
growth retardtion and failure to thrive are the early symtoms. There is almost
always moderate to severe mental retardation. Except those that die of their
cardiac defect, they are compatible with long-term survival. Hypotonia in
infancy frequently progress toward spasticity. There are also joint contractures
and cardiac defects. Myelodysplastic changes have also been reported. The
severity of clinical manifestation may be correlated with the amount of deleted
chromosome [Ono
J et al., Clin Genet 1996 Dec;50(6):474-8 ]
·
Characteristic cranial facial features: Trigonencephaly and microcephaly are frequently
seen. Typical facial features include “carp mouth”, high arched palate,
borad and/or flat nasal bridge, micrognathia, hypertelorism, and epicanthal
folds.
·
CNS findings:
·
Malformations:
There
is no known asscoiated pattern of involvement. Abnormalities that have been
described include holoprosencephaly, pachygyria [Lin
JH et al., Am J Med Genet 1998 Feb 3;75(4):341-4
]
·
White matter changes:
Abnormality of supratentorial white matter and also been reported and include
diffuse hyperintensity of cerebral white matter with multiple high internsity
areas in deep-subcortical white matter on T2-weighted images. These findings
sugges either delay of myelination, degeneration of myelin, or vasogenic
infarctions. However, since the clinical conditions of these two patients do not
decline, the abnormal imaging finding may represent delayed myelination rather
than demyelination [Ono
J et al., 1994].
·
Ocular features:
Abnormal ophthalmic findings are an integral part of Jacobsen syndrome and
feature include retinal dysplasia, optic atrophy, retinal reduplication and
ocular coloboma.
#Joubert
Syndrome: Pathologically show multiple malformations of the
cerebellum and brain stem.
·
Genetics:
Autosomal recessive. An X-linked variant may exist.
·
Clinical features include
episodic hyperpnea, abnormal eye movements (nystagmus), ataxia, mental
retardation, and polydyctyly. Respiratory abnormalities are prominent during
neonatal period but may be absent in up to half of the cases. Antenatal
diagnosis is impossible because the syndrome is defined clinically. Ataxia and
mental retardation become manifest in late infancy and childhood, at a time when
respiratory abnormalities decrease and become undetectable. Joubert syndrome is
usually fatal.
·
Pathology:
Usually associated with agenesis or hypoplasia of the cerebellar vermis with
associated enlargement of the cisterna magna. The superior cerebellar peduncles
are almost at right angles to the brain stem (horozontal superior peduncle).
Typical umbrella shaped 4th ventricles may be seen on imaging. Additional
neuropathologic lesions include dysplastic and segmented dentate nucleus,
heterotopias of cortical cerebellar cells and nuclei, several anomnalies of
brain stem nuclei such as C-shaped dysplasia of the inferior olivary nucleus,
and absence of decussation of the pyramidal tracts. Ocular abnormalies include
choroidoretinal coloboma and retinal abnormalies. Renal abnormalities may also
be associated.
NeuroLearn NeuroHelp Malformations General Syndromes For Comment: KarMing-Fung@ouhsc.edu