Eosinophilic leukemia and idiopathic hypereosinophilic syndrome are mutually exclusive diagnoses

Chronic eosinophilic leukemias and the myeloproliferative variant of the hypereosinophilic syndrome

Among patients with hypereosinophilia, a myeloproliferative variant is recognized. In many of these patients a diagnosis of eosinophilic leukemia can be made. The molecular mechanism is often a fusion gene, incorporating part of PDGFRA or PDGFRB, encoding anaberrant tyrosine kinase. Prompt diagnosis of such cases is important since specific tyrosine kinase inhibitor therapy is indicated.

Evaluation and differential diagnosis of marked, persistent eosinophilia

Hypereosinophilic syndromes (HES) are a group of heterogeneous disorders many of which remain ill-defined. By definition, the HES must be distinguished from other disorders with persistently elevated eosinophilia with a defined cause. Although marked eosinophilia worldwide is most commonly caused by helminth (worm) infections, the diagnostic approach must include noninfectious (nonparasitic) causes of marked eosinophilia as well.

Eosinophilia in systemic mastocytosis: clinical and molecular correlates and prognostic significance

BACKGROUND

In a group of patients with systemic mastocytosis (SM), marked and sustained eosinophilia is detectable (SM-eo).

OBJECTIVE

Although the molecular defect has been defined in some cases, little is known about the impact and clinical correlates of eosinophilia.

METHODS

In a cohort of 63 patients with SM, we identified 9 with permanent eosinophilia (>1500/microL). According to the World Health Organization classification, 2 had indolent SM, 1 had smoldering SM, 2 had SM with associated chronic eosinophilic leukemia (SM-CEL), and 4 had aggressive SM.

RESULTS

SM-eo was found to be associated with a significantly reduced probability of overall and event-free survival compared with SM without eosinophilia (P < .05). In the 2 patients with SM-CEL, a CHIC2 deletion was found. By contrast, no KIT mutation at codon 816 was detectable in these patients. In the other patients with SM-eo, KIT D816V was demonstrable. The 2 patients with SM-CEL had cardiomyopathy, whereas other organ systems remained largely unaffected. By contrast, in all other patients with SM-eo, organopathy, if recorded, affected the bone marrow, liver, or/and skeletal system, but not the heart, even when eosinophilia persisted for many years.

CONCLUSIONS

The biochemical basis of eosinophilia in SM is variable and predictive for the type of organopathy.

CLINICAL IMPLICATIONS

In SM eosinophilia is of prognostic significance but is not a final diagnosis and is not invariably associated with cardiomyopathy. The latter might be restricted to cases with an associated primary eosinophilic disorder (SM-CEL).

Systemic mastocytosis (SM) associated with chronic eosinophilic leukemia (SM-CEL): Detection of FIP1L1/PDGFRα, classification by WHO criteria, and response to therapy with imatinib

Based on generally accepted criteria and the WHO-classification, a subset of patients with systemic mastocytosis (SM) have (or develop) an associated clonal hematologic non-mast cell lineage disease (SM-AHNMD). We describe a case of SM with coexisting chronic eosinophilic leukemia (SM-CEL). The patient, a 51-year-old male, was first seen in 1992 with small-sized infiltrates of spindle-shaped mast cells in his marrow, and marked eosinophilia. Retrospectively, a CHIC2 deletion and the FIP1L1/PDGFRalpha fusion gene-product were demonstrable by FISH analysis and RT-PCR, respectively. SM-associated organopathy or mediator-related symptoms were not recorded. However, the patient developed cardiomyopathy. Therapy with interferon-alpha, hydroxyurea, and corticosteroids were without effects. By contrast, therapy with imatinib was followed by a fast and sustained response with complete and stable regression of eosinophilia, drop in eosinophil cationic protein, and decrease of serum tryptase to normal levels. This case provides further evidence for the potential of co-existence of SM with a primary eosinophilic disorder (CEL) defined by the FIP1L1/PDGFRalpha fusion gene. Because of the availability of a superior targeted drug (imatinib), it is of importance to screen for FIP1L1/PDGFRalpha in suspected CEL with or without co-existing SM.

Recent advances in the diagnosis and treatment of hypereosinophilic syndromes

Hypereosinophilic syndromes (HES) are a heterogeneous group of disorders characterized by marked peripheral blood and tissue eosinophilia resulting in end organ damage. Recent advances in molecular biology and immunology have led to the identification of a number of distinct subtypes of HES with differing epidemiology, pathogenesis, and prognosis. The ability to distinguish between these HES subtypes combined with the availability of new treatment modalities, including tyrosine kinase inhibitors and monoclonal antibodies, that target specific molecules involved in disease pathogenesis have dramatically altered the approach to the diagnosis and treatment of HES.