Diagnostic Complexities of Eosinophilia

Abstract

Context.— The advent of molecular tools capable of subclassifying eosinophilia has changed the diagnostic and clinical approach to what was classically called hypereosinophilic syndrome. Objectives.— To review the etiologies of eosinophilia and to describe the current diagnostic approach to this abnormality. Data Sources.— Literature review. Conclusions.— Eosinophilia is a common, hematologic abnormality with diverse etiologies. The underlying causes can be broadly divided into reactive, clonal, and idiopathic. Classically, many cases of eosinophilia were grouped together into the umbrella category of hypereosinophilic syndrome, a clinical diagnosis of exclusion. In recent years, an improved mechanistic understanding of many eosinophilias has revolutionized the way these disorders are understood, diagnosed, and treated. As a result, specific diagnoses can now be assigned in many cases that were previously defined as hypereosinophilic syndrome. Most notably, chromosomal rearrangements, such as FIP1L1-PDGFRA fusions caused by internal deletions in chromosome 4, are now known to be associated with many chronic eosinophilic leukemias. When present, these specific molecular abnormalities predict response to directed therapies. Although an improved molecular understanding is revolutionizing the treatment of patients with rare causes of eosinophilia, it has also complicated the approach to evaluating and treating eosinophilia. Here, we review causes of eosinophilia and present a framework by which the practicing pathologist may approach this diagnostic dilemma. Finally, we consider recent cases as clinical examples of eosinophilia from a single institution, demonstrating the diversity of etiologies that must be considered.

Squamous cell carcinoma and eosinophilia in a long-term course of pansclerotic morphea

“…Furthermore, he may have had reactive eosinophilia in response to his adrenal insufficiency. Glucocorticoids inhibit proliferation of eosinophils 9. Low glucocorticoid levels in adrenal insufficiency may lead to the proliferation of eosinophils 9…”

An uncommon presentation of eosinophilic granulomatosis with polyangiitis: a case report

“…With this evidence, bone marrow aspiration seemed unnecessary. However, we decided to carry out this examination when the diagnosis was still uncertain and, given the complex spectrum of disorders related to serum eosinophilia [11], we had to exclude clonal disorders.…”

Diagnostic Challenges during Pretreatment Long-term Follow-up in a Patient with <i>FIP1L1-PDGFRA</i>-positive Eosinophilia

“…Properly characterizing the disease is important, as the success of treatment depends on the underlying etiology. Currently, eosinophilia can be divided into three types: secondary, clonal and idiopathic (1).…”

“…Establishing the etiology of blood eosinophilia, which is frequently encountered by hematologists, can be a diagnostic challenge (1). Eosinophilia may be an incidental finding and, in some cases, a transient disorder, as well as a chronic condition with various organ system involvement.…”