GAIN OF 9P IN THE PATHOGENESIS OF POLYCYTHEMIA-VERA

Polycythemia vera (PV) is a clonal stem cell disorder characterized by excessive erythrocyte production, resulting in absolute erythrocytosi s. No specific structural chromosomal abnormalities have been reported in PV to date. We have observed two cases of PV with an extra i(9)(p1 0) as the sole anomaly, and FISH analysis using a 9p-specitic chromoso me microdissection probe showed that two other PV patients previously identified as having an add( 18p) and an add(lp) as the primary change s actually carried a der(18)t(9; 18)(p 12;p 11.2) and a der( l)t(1;9)( p 12;p 12), respectively. The same FISH assay was employed to evaluate domain signals on interphase cells of 15 more cases of PV with normal karyotypes and five normal controls. Two patients were observed with a significant increase in the percentage of cells with three domain si gnals. Our results strongly indicate that an additional i(9)(p 10) is a new and recurrent primary chromosome anomaly in PV, and, in consider ation of trisomy 9 being one of the most common anomalies in PV, ampli fication of a gene or genes on 9p, but not on 9q, may play a crucial r ole in the pathogenesis of PV. (C) 1998 Wiley-Liss, Inc.