대한흉부영상의학회 Korean Society of Thoracic Radiology

Discussion

Diagnosis With Brief Discussion

Diagnosis

Acute Eosinophilic Pneumonia

Radiologic Findings

Initial chest radiograph shows diffuse subtle haziness in both lungs and increased interstitial lung markings with septal lines. HRCT scan shows smooth thickening of interlobular septae and areas of lobular ground-glass attenuation in both lungs. Small amount of bilateral pleural effusion is associated.
Diagnosis was based on (a) elevated eosinophil count on BAL fluid(70%<), (b) no evidence of infection on laboratory finding, (c) initially normal peripheral eosinophil count(6%, normal range: 0-7%) but elevation(12%) on follow-up after 4 days, and (d) prompt response to steroid treatment.

Brief Review

Idiopathic acute eosinophilic pneumonia(AEP) is clinically characterized by an acute febrile illness of 1-5 days in duration accompanied by myalgias, pleuritic chest pain, and hypoxemic respiratory failure, often requiring mechanical ventilation. The etiology of AEP is unknown. It has been suggested that it may represent acute hypersensitivity to an inhaled antigen. It is pathologically characterized by infiltration of eosinophils and mononuclear cells and edema within alveoli, bronchial walls, and to a lesser degree the interstitial space and pleura. Following diagnostic criteria of AEP were suggested by Allen et al. : (a) acute febrile illness of less than 5 days’ duration, (b) hypoxemic respiratory failure, (c) diffuse pulmonary infiltrates, (d) increased eosinophil counts in BAL fluid more than 25%, (e) no history of other infectious or atopic illness, (f) prompt and complete response to steroid therapy without relapse on withdrawl, (g) absence of parasitic, fungal, and other infection. Peripheral eosinophil count is usually normal at initial but can be elevated during the subsequent clinical course.
The predominant initial radiographic finding is diffuse bilateral reticular densities. Bilateral patchy areas of ground-glass attenuation are noted on CT scan. Smooth septal thickening and pleural effusion can be seen. A mixture of air-space and interstitial opacity can be seen. And such findings would also be seen in pneumonia caused by Mycoplasma or a virus.
AEP responds satisfactorily to steroids and patients become symptom-free with essentially normal respiratory function. The condition dose not relapse.

References

1. Allen JN, Davis WB. Eosinophilic lung diseases. Am J Respir Crit Care Med 1994;150:1423-38
2. Badesch DB, King TE Jr, Schwarz MI. Acute eosinophilic pneumonia: a hypersensitivity phenomenon? Am Rev Repir Dis 1989;139:249-52
3. Allen JN, Pacht ER, Gadek JE, Cavis WB. Acute eosinophilic pneumonia as a reversible cause of noninfectious respiratory failure. N Engl J Med 1989;321:569-74
4. Cheon JE, Lee KS, Jung GS, Chung MH, Cho YD. Acute eosinophilic pneumonia: radiographic and CT findings in six patients. AJR 1996;167:1195-9

Keywords

Lung, Eosinophilic lung disease,