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DiGeorge syndrome, also called 22q11.2 deletion syndrome, is a disorder caused by a defect in chromosome 22. It results in the poor development of several body systems. Patients with 22q11.2 DS usually have characteristic facies. Common features include the following Retrognathia or micrognathia, Long face, High and broad nasal bridge, Narrow palpebral fissures, Small teeth, Asymmetrical crying face, Downturned mouth, Short philtrum, Low-set, malformed ears, Hypertelorism Congenital heart defects, either a cleft palate or incompetence of the soft palate, and immune deficiencies are common. Patients may have short stature and occasional instances of growth hormone deficiency.
Pathophysiology
The result of the 22q11.2 deletion is a range of embryonic developmental disruptions involving the head, neck, brain, skeleton, and kidneys. Portions of the heart, head and neck, thymus, and parathyroids derive from the third and fourth pharyngeal pouches, and a developmental field defect results from the chromosomal deletion. This, in turn, leads to hypocalcemia and variable T-cell deficiency. A combined T- and B-cell deficiency may result from lack of T-helper cell function as seen in cases of complete 22q11.2DS.
Epedimology
Estimates of the incidence of 22q11.2DS (DiGeorge syndrome, DGS) range from 1 per 2000 to 1 per 4000 persons in the general population of the United States, as well as internationally. It is a frequent cause of cleft palate and congenital heart defects. Although 22q11.2DS is a congenital condition, the age at diagnosis largely depends on its severity and on the types of birth defects it causes. Thus, patients with more serious cardiac defects or hypocalcemia are diagnosed in the neonatal period. Recurrent infections usually present in patients older than 3-6 months.