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?:definition
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A chromosomal anomaly that causes a congenital malformation disorder with common features that includes cardiac defects, palatal anomalies, facial dysmorphism, developmental delay and immune deficiency. The disease has a variable clinical phenotype that ranges from mild to severe. The broad spectrum of clinical phenotypes that the syndrome encompasses was previously divided into distinct syndromes (for example DiGeorge syndrome, velocardiofacial syndrome, cardiofacial syndrome) but are now known to be identical and are referred to as 22q11.2 deletion sydrome. In most cases, the syndrome is due to a 3 million base pair (Mb) deletion on the chromosomal region 22q11.2 that is flanked by low copy number repeats. The deletion is due to a non-allelic meiotic recombination during spermatogenesis or oogenesis. The variable expression of the 22q11.2 phenotype is thought to be due to genetic modifiers on either the other 22q11.2 allele or on other chromosomes. The deletion arises de novo in 90% of the cases.
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