Constitutional pericentric inversion 9 and hematological disorders: A Korean tertiary institution's experience over eight years

Constitutional pericentric inversion of chromosome 9 [inv(9)] occurs in 0.8 to 2% of the normal population and has long been considered a normal variant. It is controversial whether inv(9) is a predisposing factor for acute leukemia (AL). The effect of inv(9) on bone marrow (BM) recovery after stem cell transplantation or chemotherapy is undetermined. Between March 2001 and December 2008, the cytogenetics of 3,809 patients with suspected hematological diseases were reviewed. Of them, 586 patients were diagnosed with AL. Constitutional inv(9) was found in 55 patients with various hematological disorders, including AL and solid tumors. The proportion of inv(9) was similar in patients with AL (8/586, 1.37%) and those without (47/3223, 1.46%; p = 1.0). Of the eight patients with AL and inv(9), one refused treatment and seven had induction chemotherapy. Four of the seven patients achieved prompt hematological recovery, but the other three failed to achieve complete hematological remission. Thus constitutional inv(9) seems not to be related independently to delayed hematological recovery. One recipient of an allogeneic peripheral blood stem cell transplantation, from an unrelated donor with constitutional inv(9), also achieved prompt hematological reconstruction, further suggesting that constitutional inv(9) has no effect on hematopoietic cells. In summary, our data suggest that constitutional inv(9) is a truly random chromosomal aberration with no apparent functional effect on hematological disorders.