Inv dup(22), del(22)(q11) and r(22) in the father of a child with DiGeorge syndrome.

We here report a unique inherited case of DiGeorge syndrome. The asymptomatic father had a mosaic karyotype with a 21q11 deletion in three different cell lines. In two of the cell lines there was an additional supernumerary inv dup(22) or an r(22), respectively. In the third cell line the del(22) was the sole anomaly. FISH analysis showed that both the inv dup(22) and the r(22) included the DGS region. We hypothesize that an inter-chromosomal recombination between inverted repeats, together with a recombination between sister chromatids during meiosis I, gave rise to a deletion of 22q11 as well as an inv dup(22) containing the DGS region. The inv dup(22) was later rearranged into a ring chromosome during mitosis which was subsequently lost during cell division, thereby resulting in three different cell lines. This is the first case reported with an inv dup(22) and a del(22)(q11) in the same cell line. Our findings support a related mechanism in the formation of these two rearrangements mediated by low-copy repeats.