22q11.2 Deletion Syndrome

Introduction

22q11.2 deletion syndrome has a prevalence of approximately 1 in 5000. It is a contiguous gene syndrome caused by a 1.5 to 3.0 Mb deletion of 22q11.2. The deletion is also referred to as DiGeorge syndrome, Shprintzen syndrome or velocardiofacial syndrome. Clinical features include developmental delay, outflow tract defects of the heart (including tetralogy of Fallot, truncus arteriosus, and interrupted aortic arch), hypocalcemia arising from parathyroid hypoplasia, and thymic hypoplasia. Facial features include cleft lip and palate, low-set ears, wide set eyes, a small jaw and a small philtrum. The majority of cases arise as a new deletion but in approximately 10% of cases the deletion is inherited from a parent.

Referral information

We accept referrals from patients with appropriate clinical features for a diagnosis of DiGeorge syndrome or from family members of known affected patients.

Technical information

Microarray testing will identify deletions of the 22q11.2 region, as well as other imbalances that may be causative of the patient’s clinical presentation; therefore this is the test of choice for the majority of proband referrals (both paediatric postnatal and prenatal).  Patients who are referred for testing following the detection of a 22q11.2 deletion in a family member are usually tested by FISH to ascertain their deletion status. Adult patients referred by a cardiologist specifically for 22q11.2 deletion testing are  usually tested by FISH. The FISH test will only determine their deletion status and will not detect any other imbalance.

Price & reporting times

NHS referrals to this service are paid for where there is an existing specialist commissioning contract for genetic testing. In other cases please contact the laboratory for prices.

Test Price (£ ex VAT) TRT *
Prenatal chorionic villus sample POA 14 cd
Prenatal amniotic fluid sample POA 14 cd
Urgent postnatal blood sample POA 14 cd
Routine postnatal blood sample POA 28 cd

Postnatal sample requirements: a blood sample taken into EDTA is required for microarray testing (1-2ml neonates, 2-5ml for children/adults). FISH testing requires a blood sample in lithium heparin (1-2ml neonates, 2-5ml for children/adults).

Test validation & quality assurance - information for users

For information on the validation and limitations of microarray testing please refer to the separate microarray page on this website. FISH testing is performed using either the TBX1 FISH probe from Kreatech Diagnostics (www.kreatech.com) or the TUPLE1 FISH probe from Abbott Molecular(www.abbottmolecular.com).

Referral guidelines

Please see our referral guidelines for more information.

OMIM Number(s) - 188400

Gene(s) - TBX1

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