Division of Hematology, Stanford Cancer Center, Stanford, California.
Am J Hematol. 2014 Mar;89(3):325-37. doi: 10.1002/ajh.23664.
The eosinophilias encompass a broad range of nonhematologic (secondary or reactive) and hematologic (primary, clonal) disorders with potential for end-organ damage.
Hypereosinophilia (HE) has generally been defined as a peripheral blood eosinophil count greater than 1,500/mm(3) and may be associated with tissue damage. After exclusion of secondary causes of eosinophilia, diagnostic evaluation of primary eosinophilias relies on a combination of morphologic review of the blood and marrow, standard cytogenetics, fluorescent in situ hybridization, flow immunocytometry, and T-cell clonality assessment to detect histopathologic or clonal evidence for an acute or chronic myeloid or lymphoproliferative disorder.
Disease prognosis relies on identifying the subtype of eosinophilia. After evaluation of secondary causes of eosinophilia, the 2008 World Health Organization establishes a semimolecular classification scheme of disease subtypes including "myeloid and lymphoid neoplasms with eosinophilia and abnormalities of PDGFRA, PDGFRB, or FGFR1', chronic eosinophilic leukemia, not otherwise specified" (CEL, NOS), lymphocyte-variant HE, and idiopathic hypereosinophilic syndrome (HES), which is a diagnosis of exclusion.
RISK-ADAPTED THERAPY: The goal of therapy is to mitigate eosinophil-mediated organ damage. For patients with milder forms of eosinophilia (e.g., <1,500/mm(3)) without symptoms or signs of organ involvement, a watch and wait approach with close-follow-up may be undertaken. Identification of rearranged PDGFRA or PDGFRB is critical because of the exquisite responsiveness of these diseases to imatinib. Corticosteroids are first-line therapy for patients with lymphocyte-variant HE and HES. Hydroxyurea and interferon-alpha have demonstrated efficacy as initial treatment and steroid-refractory cases of HES. In addition to hydroxyurea, second-line cytotoxic chemotherapy agents and hematopoietic cell transplant have been used for aggressive forms of HES and CEL with outcomes reported for limited number of patients. Although clinical trials have been performed with anti-IL-5 (mepolizumab) and anti-CD52 (alemtuzumab) antibodies, their therapeutic role in primary eosinophilic diseases and HES has yet to be established.
嗜酸性粒细胞增多症包括广泛的非血液学（继发性或反应性）和血液学（原发性、克隆性）疾病，可能导致终末器官损伤。
嗜酸性粒细胞增多症（HE）通常定义为外周血嗜酸性粒细胞计数大于 1,500/mm(3)，并可能与组织损伤有关。在排除继发性嗜酸性粒细胞增多症的原因后，原发性嗜酸性粒细胞增多症的诊断评估依赖于血液和骨髓形态学检查、标准细胞遗传学、荧光原位杂交、流式免疫细胞化学和 T 细胞克隆性评估的结合，以检测组织病理学或克隆证据急性或慢性髓系或淋巴增殖性疾病。
疾病预后依赖于识别嗜酸性粒细胞增多症的亚型。在评估继发性嗜酸性粒细胞增多症的原因后，2008 年世界卫生组织建立了一种半分子疾病亚型分类方案，包括“伴有嗜酸性粒细胞增多和 PDGFRA、PDGFRB 或 FGFR1 异常的髓系和淋巴系肿瘤”、“慢性嗜酸粒细胞白血病，非特指型”（CEL，NOS）、淋巴细胞变异型 HE 和特发性嗜酸性粒细胞综合征（HES），这是一种排除性诊断。
治疗的目的是减轻嗜酸性粒细胞介导的器官损伤。对于病情较轻的嗜酸性粒细胞增多症患者（例如，<1,500/mm(3)），没有器官受累的症状或体征，可以采用密切随访的观察等待方法。识别 PDGFRA 或 PDGFRB 的重排至关重要，因为这些疾病对伊马替尼具有极高的反应性。对于淋巴细胞变异型 HE 和 HES 患者，皮质类固醇是一线治疗药物。羟基脲和干扰素-α已被证明对 HES 的初始治疗和类固醇难治性病例有效。除了羟基脲，二线细胞毒性化疗药物和造血细胞移植已用于侵袭性 HES 和 CEL，对于有限数量的患者报告了结果。尽管已经进行了抗 IL-5（美泊利单抗）和抗 CD52（阿仑单抗）抗体的临床试验，但它们在原发性嗜酸性粒细胞疾病和 HES 中的治疗作用尚未确定。
