Alpha-thalassemia X-Linked Mental Retardation (ATR-X)
Alpha-thalassemia X-linked mental retardation (ATR-X) is
an XLMR condition caused by mutations in the ATRX/XNP gene localized to
Xq13. Males usually present with moderate mental retardation and
characteristic hypotonic facies, consisting of small head size, depressed
nasal bridge, large open mouth, large prominent lips and an inverted upper
lip. Carrier females exhibit no features, a result of highly skewed
X-inactivation. Males can sometimes exhibit hemoglobin H inclusion bodies
but this clinical test is unreliable for diagnosis purposes.
Sample requirements: ATRX testing offered in this
laboratory uses RNA as the starting nucleic acid for analysis. This
requires a peripheral blood sample collected in a Qiagen PAXgene Blood RNA
tube. The PAXgene tube contains approximately 7 milliliters of
RNA-stabilizing solution. During collection, the tube is designed to stop
filling beyond the 2-3 milliliters of blood required for analysis. As
these specialized tubes are not normally available in most clinical
settings, please contact the Molecular Diagnostic Laboratory to request a PAXgene Blood RNA tube with enclosed instructions for drawing. (Please
note: for optimal results, the specimen must be collected directly into
the PAXgene tube. Blood should not be transferred from other Vacutainer
tubes into a PAXgene tube.) Another three to five milliliters of whole
blood should also be collected in an EDTA Vacutainer (lavender top).
Transport: All samples should be shipped at room
temperature and delivered via overnight courier. (FedEx is preferred.) Do
not freeze the specimen prior to transport. It is preferable to ship
samples early in the week for delivery Monday through Friday. Please
contact JoAnne Babb or Mike Friez
(1-800-473-9411) in the Molecular Diagnostic Laboratory for details regarding
transport.
Analysis standards: Testing will be completed within
6 weeks of sample receipt. The referring party will be contacted should
delays arise. Technical staff members assess the quality and
interpretation of all test results. Following an independent analysis of
results by the Director of the Laboratory, a hard copy report will be
issued. Verbal reports with consultation are available upon request by the
referring party.
Unknown mutation:
- CPT codes: 83890,
83898 (x10), 83904 (x7), 83909 (x7), 83912
Known mutation:
- CPT codes: 83890, 83898, 83904 (x2), 83909, 83912
