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17q21.31 microdeletion syndrome is a genetic disorder characterized by intellectual disability, facial dysmorphisms and a typical behavioral phenotype. A large number of reports have been published in the literature. Among the most recent articles there are interesting reports about additional clinical findings (Chiari malformation), heredity and differential diagnosis.
Additional findings has been recently
described: Terrone et al reported actually reported the first case of 17q21.31
microdeletion syndrome associated with Chiari malformation type 1 (PMID:
22659270). Therefore it has been suggested that in patients with typical
symptoms like headache, neck pain, cerebellar signs or muscle weakness the
coexistence of a Chiari malformation may be suspected.
Regarding heredity, all individuals reported to
date with 17q21.31 microdeletion syndrome have been simplex patients, resulting
from de novo deletions. However Koolen DA et al have just reported sibling
recurrence in two independent families. In both families, the mother was
confirmed to be the parent-of-origin for the 17q21.31 deletion. It seems that a
common 17q21.31 inversion polymorphism predisposes to non-allelic homologous
recombination and thus to the microdeletion. Low-level maternal somatic or gonadal
mosaicism has been hypothesized to be the underlying cause of recurrence (PMID: 22293690). Early prenatal diagnosis in future pregnancies is therefore
recommended. The empirical recurrence risk for suspected parental gonadal
mosaicism is generally calcualted in 5% at every pregnancy.
Coming to the differential diagnosis, Wright EB
et al have reported that 17q21.31 microdeletion syndrome can share some
features with cardio-facio-cutaneous syndrome. The similarities are with the
facial traits, but the most striking one is probably with large number of naevi
and other pigmentary skin abnormalities. Coarse facial appearance, relative
macrocephaly and significant learning disabilities may also be misleading and
generate an earlier suspicion of cardio-facio-cutaneous syndrome (PMID: 21084979).
For additional entries on 17q micordeletions on AllOnGenetics, you can read the following:
References:
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