<unk>  is extremely rare, the true rate of occurrence is unknown (as it is less than 1 per 1,000,000), but there are at least 50 documented cases in the literature.
Ring chromosome 14 syndrome
Ring chromosome 20 syndrome
Smith Martin Dodd syndrome
Kaufman oculocerebrofacial syndrome
13q deletion syndrome
2q37 deletion syndrome
22q11.2 duplication syndrome
8p23.1 duplication syndrome