DiGeorge syndrome and related birth defects

Classically, DiGeorge syndrome patients have congenital heart defects, particularly involving the outflow tract, hypocalcaemia, cell-mediated immune deficiency, learning or behavioural problems, craniofacial dysmorphism and hemizygosity for a region of human chromosome 22q11. This chromosomal abnormality is now known to cause other syndromal defects and apparently isolated congenital heart disease. Although most patients have a large deletion, at least 2 Mb, a critical region of 300 kbp has been defined. Within this region a putative transcriptional regulator called TUPLE-1 has been identified. TUPLE-1 is proposed as a candidate gene for the 22q11 haploinsufficiency syndromes.