Recurrent der(9;18) in essential thrombocythemia with JAK2 V617F is highly linked to myelofibrosis development.

We studied JAK2 mutational status, in combination with cytogenetic analysis in 54 patients with essential thrombocythemia (ET), and attempted to obtain greater insight into the correlation between clinicohematologic features and genetic abnormalities. We found that six ET patients developed myelofibrosis and four of them had JAK2 V617F mutation. It is noteworthy that three of the four ET patients with JAK2 V617F had add(18)(p11). In contrast, the remaining two ET patients who developed myelofibrosis had neither JAK2 V617F nor add(18)(p11). Moreover, none of the ET patients with JAK2 V617F and chromosome changes other than add(18)(p11) developed myelofibrosis. The current results indicate that add(18)(p11), possibly due to der(9;18), may contribute a link to myelofibrosis in JAK2 V617F-positive ET patients, while those with wild-type JAK2 may use another pathway toward myelofibrosis.