De Novo Pericentric Inversion of Chromosome 9 Inv (P12;Q13) and Intellectual Disability: Case Report and Literature Review

Abstract

The inversionofpericentric type in chromosome 9 is one of the most common (1–3%) chromosomal aberrations in normal and mentally retarded individuals thatoccurs in heterochromatin region of this chromosome. In this investigation, chromosomal analysis after conventional G-banding unveiled a pericentric inversion of chromosome 9 in an intellectually disabled seven years male child.The parents had the normal karyotypes that indicated de novo origin of this anomaly.The patient's partial duplication for chromosome 9 is due to crossing over occurring within the inverted segment during reductional division and retention occurs through Mendelian inheritance without any phenotypic abnormalities. The degree of mental retardation was found to be moderate (IQ: 40-45 to 50-55). In this article, the information related to inversion of chromosome 9 is reviewedand possible significance of this anomaly is also discussed.