Eosinophilia (호산구증)

Eosinophilia (호산구증)

Definition

Pathophysiology

  - Primarily tissue-dwelling cells

혈액보다 조직에 수 백배 더 많이 존재하기 때문에, 말초 혈액에 있는 eosinophilia 로는 organ damage의 risk 를 예측하지 못한다. (정확하게 반영하는 것이 아니다.)

  - Target organs

주로 Skin, lung, GI tract 가 되고, Cardiac, Nervous system 에 involve 할 경우 Life threatening 할 수 있다.

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Major cause

Degree of eosinophilia는 양극단을 제외하고는 별로 진단에 도움이 안된다.

  - Very mild eosinophilia : Asthma or allergic rhinitis 등

  - Very severe eosinophilia (2만개 이상…) : Myeloproliferative neoplasm 등

* Hypereosinophilia (HE)

  - 1500개 이상 (1달이상 간격 두고 2회 이상 측정)

  - And/or pathologic confirmation of tissue HE

* Hypereosinophilic syndrome

  --> HE + Eosinophil-mediated organ damage and/or dysfunction

(1) Primary (or neoplastic) HES

(2) Secondary (or reactive) HES

   : driven by overproduction of eosinophilopoietic cytokines (e.g. IL-5) by other cell types, polyclonal

(3) Idiopathic HES

(4) Specific syndromes associated with HE

   : eosinophilic granulomatosis and polyangiitis (EGPA) and certain immunodeficiencies

(5) Hypereosinophilia of undetermined significance (HEUS)

   :  persistent unexplained HE, but without apparent complications related to tissue eosinophilia

* T cell lymphocytic variants

Lymphocytic variant HES (L-HES) is characterized by a predominance of skin and soft tissue involvement, although other clinical manifestations of HES, including cardiovascular, pulmonary, and rheumatological/articular involvement, are also present. 

In this variant, which is classified as a subvariant of secondary/reactive HES, IL-5-producing T cell subsets have been identified in the peripheral blood. 

The most frequently reported abnormal T cell phenotype in L-HES is CD3-CD4+. 

In the largest cohort of patients with CD3-CD4+ associated L-HES reported, the majority of patients had elevated serum immunoglobulin E (IgE), skin involvement, and lymphadenopathy. 

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Total lymphocyte counts were elevated in just one-third of patients. The prevalence of this variant among all patients with HES is not well-defined. In one series of 60 patients with idiopathic eosinophilia, 16 were found to have abnormal IL-5-producing T cells. This disorder may evolve to lymphoma.

In addition to IL-5, the abnormal T cells produce other T helper type 2 (Th2) cytokines such as IL-4 and IL-13, as well as GM-CSF. The effects of these Th2 cytokines on other cells (eg, B cells) account for associated biologic features of L-HES. Indeed, B cell stimulation leads to increased IgE synthesis and polyclonal hypergammaglobulinemia.

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2018. 9. 3 - SJH