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DiGeorge syndrome is characterised by the association of several malformations: hypoplastic thymus and parathyroid glands, congenital conotruncal cardiopathy, and a subtle but characteristic facial dysmorphology. Velocardiofacial syndrome is marked by the association of congenital conotruncal heart defects, cleft palate or velar insufficiency, facial dysmorpholgy and learning difficulties. It is now accepted that these two syndromes represent two forms of clinical expression of the same entity manifesting at different stages of life. The characteristics defining these syndromes overlap with those of microdeletion 22q11. The acronym CATCH 22 was proposed to describe the clinical features of microdeletion 22q11 (Cardiac-Abnormal face-Thymus-Cleft palate-Hypocalcemia). The clinical course of the syndrome is mainly determined by the nature of the congenital malformations involved. The hypocalcemia frequently observed in the neonatal period generally disappears, but some children may have persistent hypoparathyroidism, which requires treatment. The velopharyngeal insufficiency often results in nasal speech, even in the absence of cleft palate, and may be associated with language difficulties. Microdeletion in 22q11 is present in 95% of patients. The incidence of the microdeletion in 22q11 in the general population is estimated at 1 in 5000 births. In 10 to 20% of cases, the 22q11 microdeletion is transmitted in an autosomal dominant manner, with one of the parents being a carrier of the microdeletion. However, in the majority of cases, the chromosome anomaly arises de novo.
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