INTRODUCTION —

1. 首先在1989年,於acute  resp. failure的case中被描述。

2. AEP與CEP不同,雖然都是肺實質有eosinophilic infiltration

ETIOLOGY — cause unknown, 可能是對unidentified inhaled antigen有 acute hypersensitivity reaction。新抽菸者要考慮之。

PATHOLOGY — (資料不多,參考Mayo clinic的study)

1. Severe extent of disease (肺表面有75%以上的不正常)

2. 常見DAD (Acute and organizing diffuse alveolar damage); 會有 Hyaline membranes & interstitial widening (由於edema, fibroblast proliferation, 與inflammatory cells,以上這些是DAD 在organizing phase的表現)。

3. Marked numbers of interstitial and lesser numbers of alveolar eosinophils were found in all samples?? (不懂)

4. 其他可能的表現有: type II pneumocyte hyperplasia (55%), interstitial lymphocytes (100%), organizing intraalveolar fibrinous exudate (100%), perivascular and intramural inflammation without necrosis (33%)

5. 沒有Granulomas或alveolar hemorrhage。

CLINICAL FEATURES — 會出現於any age,甚至是healthy children。大部份病人約在20~40歲之間。男性居多, 是女性兩倍。少部份有過敏疾病。

1. Clinical presentation: 

 (1) acute illness(小於四週);大部份症狀少於七天。症狀包括:乾咳(95%), 喘(92%),與發燒(88%),另外也會有malaise, myalgias, night sweats, chills, and pleuritic chest pain。

 (2) Physical examination: fever (often high), tachypnea,  bibasilar inspiratory crackles, occasionally rhonchi。少見Clubbing and signs of cor pulmonale. 

 (3) 可能一開始就hypoxemic respiratory insufficiency, 需要插管。

2. Laboratory features: 起初可能有neutrophilic leukocytosis;大多病人一開始 eosinophil fraction不會高,接會突然高起來。另外ESR與CRP有時也有會高。大部份病人IgE會高。

EVALUATION — 我們會為AEP的病人會有漸近性的喘(一個月內), 而且chest radiograph有diffuse parenchymal opacities。要問用藥史(如cocaine, gemcitabineinfliximabranitidinevenlafaxine), 照過R/T,有寄生蟲/fungus。

1. Laboratory studies: 通常沒啥用。只能用排除其他疾病。

(1)ANCA test for granulomatosis with polyangiitis (Wegener’s) or eosinophilic granulomatosis with polyangiitis (EGPA, Churg Strauss)。但EGPA只有40 to 60%陽性。

(2)IgM and IgG specific for Coccidioides.

(3)Strongyloides or Paragonimiasis

2. Imaging:

(1) 最開始時,only subtle reticular / GGO + Kerley B lines => 疾病進展,bilateral diffuse mixed GGO (也可能會進展成consolidation, 隨機分佈,但疾病惡化後會沿著bronchovascular bundles走) + reticular opacities (共同組成會有crazing paving的感覺);也可能只有GGO (25%) 或reticular (25%)

(2) diffuse distribution of opacities (重要!!: 不像CEP的分佈: the opacities localized to the lung periphery)

(3) Small pleural effusions are common (70%,後來可能到90%) / bilateral (interstitial 是smooth的)

3. Pulmonary function tests: 進展太快,無法獲得PFT。若辦到了-> restrictive process (reduced FVC & TLC + a normal FEV1/FVC); reduced DLCO

DIAGNOSIS — 

(1)主要靠BAL加排除known causes of pulmonary eosinophilia;不太需要lung biopsy

(2)Diagnostic criteria — 

a. A febrile illness of short duration (one month or less, but often less than one week)

b. Hypoxemic respiratory failure (eg, pulse oxygen saturation [SpO2] <90 percent on room air or arterial oxygen tension [PaO2] <60 mmHg)

c. Diffuse pulmonary opacities on chest radiograph

d. BAL differential cell count showing eosinophilia >25 percent

e. Absence of known causes of eosinophilic pneumonia, including drugs, infections, asthma, or atopic disease (table 1) (see "Causes of pulmonary eosinophilia")


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