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22q11.2 Deletion Syndrome – Definition and Diagnosis

22q11.2 deletion syndrome is a syndrome caused by deletion of a small piece of chromosome 22 at a location designated as q11.2, close to the center of the chromosome. DiGeorge syndrome is commonly known as 22q11.2 deletion syndrome.

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Definition and Diagnosis of 22q11.2 Deletion Syndrome

New York (USA), June 16, 2013

Definition of 22q11.2 Deletion Syndrome

22q11.2 deletion syndrome is a syndrome caused by deletion of a small piece of chromosome 22 at a location designated as q11.2, close to the center of the chromosome. This location is specifically on region 1, band 1, and sub-band 2 on long arm of one of the pair of chromosomes 22.

Pediatric endocrinologist Angelo DiGeorge first described 22q11.2 deletion syndrome.

What is 22q11.2 Deletion Syndrome?

22q11.2 deletion syndrome is same as DiGeorge anomaly, DiGeorge syndrome (DGS), Shprintzen syndrome, conotruncal anomaly face syndrome, velo-cardio-facial syndrome, congenital thymic aplasia, third and fourth pharyngeal pouch syndrome, strong syndrome, and thymic hypoplasia.

In recent times, DiGeorge disorder or DiGeorge syndrome is commonly known as 22q11.2 deletion syndrome.

22q11.2 deletion syndrome is a birth defect and occurs in around one in four thousand or six thousand cases.

22q11.2 deletion syndrome affects child’s immune system as thymus and parathyroid glands are either absent or underdeveloped.

22q11.2 deletion syndrome causes various medical problems like cleft palate, heart defects, behavioral disorders, and low calcium levels in blood, although severity differs.

Diagnosis of 22q11.2 Deletion Syndrome

Diagnosis Before Birth
Ultrasound examination in the eighteenth week of pregnancy can detect abnormalities in palate or heart development.

FISH or fluorescence in situ hybridization is a technique to detect 22q11.2 deletion syndrome before birth. This diagnostic test is conducted on cell samples or DNA probes from 22q11.2 deletion syndrome region on chromosome 22. Samples are collected through amniocentesis in the fourteenth week of pregnancy. FISH delivers correct results in around 95% cases.

Diagnosis After Birth
Doctors suggest diagnosis of 22q11.2 deletion syndrome soon after noticing baby’s facial features at birth. Further confirmation is done through blood tests for phosphorus, calcium, and parathyroid hormone levels. Sheep cell test detects abnormalities in immune system functions. Abnormal location or absence of thymus gland is sometimes detected during heart surgeries.

Doctors often advise detailed tests for diagnosing 22q11.2 deletion syndrome, as symptoms are not typical across all cases.

In most cases, 22q11.2 deletion syndrome is not inherited. It occurs as a random event in early stages of development of fetus or during formation of reproductive cells.

In very few cases, as low as ten percent, 22q11.2 deletion syndrome is inherited from an affected parent.

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