Eosinophilia in mast cell disease

Abstract

Eosinophils and mast cells coexist in clonal and nonclonal disorders. The interplay between these cells is complex and not fully understood. Discussed are both allergic/nonclonal disorders in which both cell types are increased in number are likely to play a role in pathogenesis and clonal disorders in which both cell types are affected and play key roles in pathogenesis. Finally, some treatment options, keeping both disorders in mind, are discussed. Future directions in thinking about these disorders are also briefly explored.

Keywords: Chronic eosinophilic leukemia (CEL); Eosinophilia; FIP1L1-PDGFRA fusion; Hypereosinophilic syndrome; Imatinib; Systemic mastocytosis; Tryptase.

Fig. 1

Workup of uncharacterized eosinophilia. 1. World Health Organization criteria for systemic mastocytosis (see Box 1). 2. Tyrosine kinase mutations in chronic eosinophilic leukemia. Including but not limited to FIP1L1-PDGFRA fusion, fusion of PDGFRA with other partner genes, fusions involving PDGFRB. 3. Formerly known as Churg-Strauss syndrome.

Fig. 2

Bone marrow biopsy and aspirate in a patient with chronic eosinophilic leukemia carrying the FIP1L1-PDGFRA rearrangement. Increased numbers of hypogranulated neoplastic eosinophils are observed in the aspirate (A, B) (Wright-Giemsa, original magnification ×100). The infiltrate predominantly consists of eosinophils in a background of fibrosis in the biopsy (C, D) (Hematoxylin and Eosin, original magnification ×400) as opposed to mastocytosis whereby the predominant infiltrate is that of mast cells. (Courtesy of German A. Pihan, MD, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA.)

Fig. 3

(A) Bone marrow biopsy in systemic mastocytosis, intermediate magnification (Hematoxylin and Eosin, 100×) featuring atypical, spindle-shaped mast cells and intermingled eosinophils surrounding a lymphoid aggregate. (B) Bone marrow biopsy in systemic mastocytosis, high magnification (Hematoxylin and Eosin, 400×) showing atypical, spindle-shaped mast cells (M) with numerous intermingled eosinophils (E). (Courtesy of Charles W. Ross, MD, University of Michigan, Ann Arbor, MI.)