A small paracentric inversion of chromosome 18, inv(18) (q22.1q23), in a woman with multiple congenital anomalies and mental retardation

We report on a 42 year old woman with the smallest reported paracentric inversion of chromosome 18, with the karyotype 46,XX,inv(18)(q22.1q23). The patient shows some of the features often seen in 18q- syndrome patients including short stature, developmental delays, mental retardation, midface hypoplasia, upslanting palpebral fissures, sparse hair, atretic ear canals, mild conductive hearing loss, and aggressiveness. Although cytogenetically it appears that no chromosomal material is lost, FISH studies using an 18q telomeric probe showed that chromosomal material comprising part of band 18q23 is lost. Further molecular studies showed the MBP gene, which maps to 18q23, was missing. We suggest that all chromosome inversions involving telomeric regions be evaluated by telomere FISH probes for deletion.