Molecular Genetics Clinical Laboratory-
Angelman syndrome presents in early childhood with
hypotonia followed by motor and intellectual retardation. Affected children are
ataxic, epileptic, have absence of speech, and an unusual facies characterized
by a large mandible and an open-mouthed expression. Patients demonstrate
excessive laughter, an occipital groove, a facility for protruding the tongue,
abnormal choroidal pigmentation, and characteristic electroencephalogram (EEG)
discharges. This disorder is caused by deletions of chromosome 15q11-q12 (~70%
of cases) by uniparental paternal disomy of chromosome 15 (~5%), by mutations in
the UBE3A gene (~20%) or by unknown etiology (~5%).
Testing is done using molecular
cytogenetic FISH analysis with SNRPN, & D15S10 probes and a routine
karyotype in the Cytogenetics Laboratory, as well as SNRPN gene methylation
testing and molecular polymorphism analysis in the Molecular Genetic Laboratory.
Specimens from parents are requested for UPD analysis.
Most testing is completed within a time
of 21 days following specimen receipt. Prenatal testing is usually completed
within 7 days from specimen receipt.
All specimens should be kept at
room temperature and shipped overnight in an insulated container.
Adults and Children:
Two tubes of whole blood are
1) A tube of 4 cc whole blood collected in an EDTA (lavender top)
tube is preferred. Whole blood collected with other anticoagulents is acceptable
but not preferred.
2) A second tube with 3 cc of blood collected in sodium heparin (green top)
tube is required. Lithium heparin and other anticoagulants are not acceptable.
The minimum specimen is 0.5 cc whole blood in
EDTA tube and 2.0 cc of blood in a sodium heparin (green top) tube.
Prenatal testing is usually not indicated since
most cases of Angelman syndrome, except those with chromosomal rearrangements,
are de novo and have a low risk for future pregnancies. Genetic counseling is
Charges are available upon request.
FOR MORE INFORMATION, PLEASE CONTACT:
(727) 767-8611 (Director)