Atypical microdeletion 22q11.2 in a patient with tetralogy of Fallot

The 22q11.2 microdeletion syndrome (22q11.2 DGS) is characterized by an extreme intrafamilial and interfamilial variability. The main clinical features are congenital heart defects, palatal abnormalities, learning disability, facial dysmorphisms and immune deficiency. In 85-90% of cases, the 22q11.2 DGS is caused by a heterozygous ~3-Mb deletion, including the TBX1 gene, considered one of the major genes responsible for heart defects. Individuals with atypical deletions with at least one breakpoint outside low copy repeats have been reported. Our patient is a child presenting tetralogy of Fallot (TOF) with an atypical 22q11.2 deletion proximal to the critical DiGeorge region. The rearrangement was inherited from the healthy mother and spanned ~642-970 kb, encompassing DGCR6 and PRODH, two novel possible candidate genes for conotruncal heart defects.