PB1960 CHRONIC MYELOID LEUKEMIA DEVELOPING AFTER SYSTEMIC MASTOCYTOSIS: FAST AND COMPLETE MOLECULAR RESPONSE INDUCED BY IMATINIB

• Published in: HemaSphere 2019-06, Vol.3 (S1), p.890-891
• Main Authors: Savchuk, A., Cabrera, W., Sola, E., Cornago, J., Del Campo, J.F., López‐Pereira, P., Orfao, A., Álvarez‐Twose, I., Steegmann, J.L.
• Format: Article
• Language: English
• ISSN: 2572-9241; 2572-9241
• DOI: 10.1097/01.HS9.0000566336.28751.9f

Background: We present here the case of a 52 year old male patient who was diagnosed of D816 V + indolent systemic mastocytosis in 2006. The patient received only symptomatic treatment with fexofenadine, sodium cromoglycate, and ranitidine. In November 7th 2016, mild leukocytosis was detected in one of the screenings. The patient had not symptoms or signs of CML or mastocytosis. WBC was 14.04 x 109/L, Hb: 15,5 g/dl; Platelet 832 x 109/L. Serum tryptase was normal (5.4 ng/ml). led to the diagnosis of Ph1+, BCR‐ABL, e14a2 positive CML. Cytologic exam of the bone marrow (BM) disclosed a typical picture of chronic phase of CML and 0.2% mastocytes. Karyotyping disclosed typical t(9;22) in 95% of the BM metaphases. Mutational analysis. Mastocytes and CD34+ cells were sorted by FACSAria. The mutation D816 V (pAsp816/Val) was assessed by PNA‐PCR and NGS, and was not detected either in CD34+ cells, or in mastocytes (this last result being not conclusive, because of the low number of mastocytes present in the BM (675 cells). Jak2V617F was not present.BCR‐ABL detection. RT‐PCR in BM disclosed e14a2 transcript. FISH analysis was performed in the sorted populations, and was detected in CD34+ (84%), Monocytes (61%), neutrophils (88%), eosinophils (73%), and mesenchymal cells (16%). It was negative in lymphocytes, and although 8 out of 18 mastocytes were positive, this percentage was inconclusive. Aims: To describe an extremely rare case of Chronic myeloid leukemia developing after systemic mastocytosis. Methods: NA Results: Hydrea was used from January 10 th to April 21 st 2017, and Imatinib 400 QD was started four days later.Table 1 depicts the evolution of molecular response. The treatment obtained major molecular response, MR4, and MR5 in 3, 6 and 9 months respectively.MR5 was sustained at 18 months of imatinib treatment. Serum tryptase diminished, probably because of the effect of imatinib on wild‐type c‐Kit.AEs were all of grade 1, and included eye‐lid edema, weight gain, and vomiting. Summary/Conclusion: The case here described is the second case reported of CML arising in a patient with D816 V mastocytosis. In 2005, Agis et al reported one case of typical CML with concurrent systemic, D816 V mastocytosis. In that case Imatinib treatment resulted in complete cytogenetic response 1. In our case, in spite of the presence of mastocytes in BM, we did not detect either the D816 V mutation, or the BCR‐ABL signal in the mastocytes. The absence of D816 V in CD34 cells sup