Editor—Carriers of paracentric chromosome inversions are usually regarded as being at low risk of having offspring with an unbalanced chromosome complement.1 2Some reports have suggested that rearrangements, such as very small interstitial deletions or duplications arising from unequal crossing over at the base of the inversion loop and deletion or deletion/duplication recombinants, created by the breakage of an unstable dicentric chromosome, can arise from paracentric inversions.3-7 Pettenati et al 8 reviewed 446 cases of paracentric inversions and suggested that carriers of such inversions had a 3.8% risk of having viable offspring with stable recombinant chromosomes. However, this observation has been disputed9 as it is possible that so called paracentric inversions giving rise to monocentric recombinants are actually insertional translocations and the traditional view is that the resulting unbalanced chromosomes arising from a paracentric inversion would involve either a dicentric or acentric chromosome, and therefore be unlikely to be viable.10

We report a liveborn child with mild dysmorphic features who had a dicentric chromosome arising from a maternal paracentric inversion. To our knowledge there have only been two previous reports of this …