Correlation of clinical phenotype with a pericentric inversion of chromosome 9 and genetic counseling.

OBJECTIVE To describe the history of 157 carriers of pericentric inversions on chromosome 9 [inv9] with karyotype analyses and evaluate the significance of these findings. METHODS We studied the incidence, clinical significance, and genetic counseling of inv9 p11;q12, p11;q13, and p11;q21 patients who were referred to our laboratory from various clinics of the Medical Faculty, Cukurova University, Adana, Turkey retrospectively from 157 cases of 15528 cytogenetic analyses collected between May 1993 and February 2007. RESULTS We found the incidence of inv9 to be 1.01%. From a review of 157 cases with inv9, it is concluded that the incidence of the spontaneous abortion group 30.6% appeared to be high among the adult patients with inv9. The 17 cases were found to have mental retardation, which gave an incidence of 10.8%. We here report the clinical and cytogenetic findings of 157 inv9 cases that had different problems. CONCLUSION Although, inv9 has been considered to be a normal variant, our observation implies a possible association between inv9 and abnormalities, suggesting that a susceptibility locus for these phenotypes may be located at the breakpoint of the inversion on chromosome 9, which may lead to cloning of a susceptibility gene for unspecified abnormalities. These findings could be used widely in clinical genetics, and as an effective tool for genetic counseling and reproductive guidance.