The syndrome is caused by genetic deletions (loss of a small part of the genetic material) found on the long arm of one of the two 22nd chromosomes. Very rarely, patients with somewhat similar clinical features may have deletions on the short arm of chromosome 10.
The mechanism that causes all of the associated features of the syndrome is unknown. 22q11.2 deletion syndrome may involve migration defects of neural crest-derived tissues, particularly affecting development of the third and fourth branchial pouches (pharyngeal pouches). This affects the thymus gland; a mediastinal organ largely responsible for differentiation and induction of tolerance in T-cells, and the Parathyroid glands, responsible for regulation of blood calcium levels.
Read more about this topic: Di George Syndrome
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