Center for Human Genetics and Laboratory Diagnostics, Dr. Klein, Dr. Rost and Colleagues

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DiGeorge Syndrome (DGS), Mikrodeletion 22q11.2 [Q93]

OMIM number: 188400

Dr. med. Imma Rost

Scientific Background

The DiGeorge syndrome arises from a developmental field defect of the 3rd and 4th pharyngeal pouches and the intervening 4th pharyngeal arch and their derived structures such as the thymus and the parathyroid gland. Therefore, the signs and symptoms include thymus hypo- or aplasia causing impairment of cellular immunity. Approx. 10% of all affected patients exhibit a severe immunodeficiency. Approx. 60% exhibit hypoplasia of the parathyroid glands that may cause hypocalcemia, sometimes accompanied by seizures. The hypocalcemia usually has its onset in the newborn; however it may also occur later. Spontaneous normalization of the serum calcium level is possible at any time, yet, a long-term calcium substitution is usually necessary. Cardiac defects are another cardinal feature of DGS. They mainly comprise abnormalities of the aortic arch, conotruncal cardiac defects such as tetralogy of Fallot or truncus arteriosus communis as well as ventricular septal defects or patent ductus arteriosus. Cleft palates may occur. A hoarse voice or, in later stages, nasal speech are signs of velopharyngeal insufficiency.

Almost all patients exhibit a mild intellectual disability, in approx. 30 to 40% short stature is observed. Physical signs include hypertelorism, epicanthal folds, a small mouth with everted upper lip, microretrognathia and low-set, malformed ears.

The DGS represents only one part of the very variable clinical spectrum of the microdeletion 22q11.2. In approximately 5 to 10% of all cases, the microdeletion 22q11.2 is inherited from one parent. Especially if there is desire for another child, genetic testing of the parents of the affected child is recommended.