Refractory anaemia with hypereosinophilia and clonal abnormal metaphases detected only in the neutrophilic granulopoietic series

Case 32. Eosinophilia: Reactive or neoplastic?

A diagnosis of eosinophilic leukemia was suspected in a patient who presented with eosinophilia and a mild macrocytic anemia and was found to have trisomy 8. Further tests and the subsequent clinical course permitted an accurate diagnosis.

Imatinib therapy for hypereosinophilic syndrome and eosinophilia-associated myeloproliferative disorders

A pathogenetic mutation, FIP1L1-PDGFRA, that results from an interstitial chromosome 4q12 deletion, leads to a constitutive activation of the platelet-derived growth factor receptor-alpha (PDGFRA) tyrosine kinase as well as a disease phenotype that mimics both the hypereosinophilic syndrome (HES) and systemic mast cell disease associated with eosinophilia (SMCD-eos). Complete remissions, in response to treatment with low-dose imatinib mesylate (100 mg/day or less) have now been documented in all cases of FIP1L1-PDGFRA(+) eosinophilic disorder as well as other eosinophilic disorders that carry activation mutations of the PDGFRB gene that is located on chromosome 5q33. Furthermore, response to therapy has been rapid (within days) and durable. Interestingly, imatinib mesylate treatment, at a higher dose level (400 mg/day), might induce either partial or short-lived complete remissions in HES that is not associated with the aforementioned PDGFR mutations. These observations make it necessary to re-examine current disease classification and treatment algorithms in eosinophilic disorders.

Cloning of the t(1;5)(q23;q33) in a myeloproliferative disorder associated with eosinophilia: involvement of PDGFRB and response to imatinib

Eosinophilia is common in myeloproliferative disorders (MPDs) with abnormalities of chromosome band 5q31-33, including those that present with t(1;5)(q23;q33). With the development of rational drug therapy, characterization of the molecular targets for these translocations could guide treatment and affect patient survival. We cloned the t(1;5)(q23;q33) and showed that it fuses platelet-derived growth factor receptor beta (PDGFRB) to the coiled-coil domains of a novel partner protein, myomegalin. Using two-color interphase fluorescence in situ hybridization (FISH), we also demonstrated that the eosinophils are clonal in these disorders. Imatinib mesylate has recently been shown to be efficacious in MPDs with PDGFR activation. Therefore, following our molecular studies, we were able to redirect this patient's treatment. Although she had refractory and progressive disease, once imatinib was started, complete clinical and hematologic remission, as well as major cytogenetic response, was achieved. Given the therapeutic implications, our findings stress the need to aggressively investigate the molecular basis of these diseases, with emphasis on the PDGFR family.

Prevalence and clinical characteristics of myelodysplastic syndrome with bone marrow eosinophilia or basophilia

By retrospectively analyzing 288 patients with de novo myelodysplastic syndrome (MDS), we sought to determine the prevalence and clinical characteristics of bone marrow eosinophilia and basophilia that were detected at presentation. Bone marrow eosinophilia and basophilia were defined as a differential count of each cell type exceeding 5.0% and 1.0%, respectively. Of 288 patients with MDS, 36 (12.5%) fulfilled this criterion for bone marrow eosinophilia (MDS-Eos); 34 patients (11.8%) showed basophilia (MDS-Bas), and 11 (3.8%) satisfied both criteria (MDS-EosBas). The remaining 229 patients had neither eosinophilia nor basophilia in their bone marrow (MDS(-/-)) at presentation. Cytogenetic analysis was carried out on unstimulated bone marrow cells obtained from 264 patients. When the cytogenetic categorization of the IPSS (International Prognostic Scoring System) for MDS was applied, significantly higher numbers of MDS-Eos and MDS-Bas patients had chromosomal abnormalities carrying intermediate or poor prognosis, compared with the MDS(-/-) patients. Specific chromosomal abnormalities and complex karyotypes were associated with MDS-Eos and/or MDS-Bas. In accordance with these results, the overall survival rate was significantly lower, and the evolution to acute myelogenous leukemia (AML) occurred more frequently in the MDS-Eos and MDS-Bas than in the MDS(-/-) patients. Multivariate analysis demonstrated that bone marrow basophilia was an independent risk factor for evolution to AML. Our study indicates that bone marrow eosinophilia and basophilia in patients with MDS predict a poorer prognosis.

The relationship between the myelodysplastic syndromes and the myeloproliferative disorders

As a result of clonal evolution typical cases of one of the myelodysplastic syndromes may develop myeloproliferative features. Similarly, typical cases of one of the myeloproliferative disorders may develop dysplastic features, either as part of the natural history of the disease or as a result of exposure to mutagenic drugs or isotopes. There is also an important group of "overlap syndromes" in which cases, at presentation, have both dysplastic and proliferative features. Chronic myelomonocytic leukaemia and many cases of atypical chronic myeloid leukaemia, juvenile chronic myeloid leukaemia and the childhood monosomy 7 syndrome are "overlap syndromes". In addition, a significant minority of cases which fit the generally agreed criteria for a diagnosis of one of the myelodysplastic syndromes (refractory anaemia, refractory anaemia with ring sideroblasts or refractory anaemia with excess of blasts) also have thrombocytosis, neutrophilia, monocytosis, eosinophilia or basophilia.

Polychondritis Terminating in Eosinophilic Leukemia

We report here on a patient presenting with Relapsing Polychondritis (RP) two years before the diagnosis of Myelodysplasia (MDS) terminating in Eosinophilic Leukemia (EoL). The evolution of RP several etiology of RP in this patient. The terminal development of EoL in our case is assumed to represent clonal evolution caused by a second mutagenic event. The existence of autoimmune skin disorders in both the patient and his offspring (vitiligo and subacute cutaneous lupus erythematosus, respectively) implies that the coexistence of MDS and RP may have been caused by a functional disturbance of the immune system.