The JAK2-V617F mutation and essential thrombocythemia features in a subset of patients with refractory anemia with ring sideroblasts (RARS)

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Abstract
Sixteen patients diagnosed with RARS over a period of 20 years (1986-2005) and who subsequently presented with thrombocytosis were examined. Genomic DNA was prepared from blood granulocytes (2 patients) or stained bone marrow smears (14 patients) collected at the time of thrombocytosis. Quantitative PCRs were performed with forward primers 5′-GCGCGGTTTTAAATTATGGAGTATGTG-3′ (wild-type JAK2) and 5′-GCGCGGTTTTAAATTATGGAGTATGTT-3′ (JAK2-V617F), reverse primer 5′-GCGGTGATCCTGAAACTGAATTTTC-3′ and 6-FAM probe 5′-TGGAGACGAGAGTAAGTAAAACTACAGGCT-3′ as described elsewhere.6 Wild-type JAK2 was amplified successfully for the 16 patients; JAK2-V617F was amplified for 5 patients. As observed in ET,6 the level of expression of JAK2-V617F was less than 40% of total JAK2 (median, 16%; range, 4%-35%). For 1 patient, JAK2-V617F was also amplified from a bone marrow smear performed 5 years earlier, at a time when platelet counts were normal.