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

OBJECTIVES: To describe the history of 157 carriers of pericentric inversions on chromosome 9 [inv(9)] with karyotype analyses and evaluate the significance of these findings.

METHODS: We studied the incidence, clinical significance, and genetic counseling of inv(9) (pll;q12), (pll;q13), and (pll;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 inv(9) to be 1.01 %. From a review of 157 cases with inv(9), it is concluded that the incidence of the spontaneous abortion group (30.6%) appeared to be high among the adult patients with inv(9). 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 inv(9) cases that had different problems.

CONCLUSION: Although, inv(9) has been considered to be a normal variant, our observation implies a possible association between inv(9) 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.