Case In Point: Acute eosinophilic pneumonia in a 19-year-old man

The case

A previously healthy 19-year-old man was referred to our hospital with acute respiratory distress. Over the past 8 months, he had worked in a factory, with some exposure to plastic material but with no exposure to fumes. He started smoking several cigars per day 2 weeks before admission. A productive cough, dyspnea, and fever (temperature, 38.5°C [101.3°F]) developed 2 days before admission.

On admission, the patient was febrile (temperature, 38.6°C [101.5°F]). Auscultation revealed bilateral crackles in the late inspiratory phase. The results of the rest of the physical examination were normal. Arterial blood gas determination on nonrebreather mask revealed a pH of 7.43, PaO₂ of 69 mm Hg, and PaCO₂ of 32 mm Hg. The patient was then intubated.

His peripheral white blood cell (WBC) count was 13,600/µL, with 81% neutrophils and 5% eosinophils. A chest radiograph revealed diffuse bilateral pulmonary infiltrates (Figure 1). A chest CT scan showed ground-glass opacities, mainly in dependent regions of the lungs (Figure 2).

BAL was performed. In the BAL fluid, marked eosinophilia (74%) was observed. BAL fluid and stool cultures were negative for common bacteria, fungi, and parasites. HIV test results were negative.

Discussion

AEP is an idiopathic form of respiratory failure characterized by very high numbers of alveolar eosinophils without significant blood eosinophilia. Severe respiratory failure can develop rapidly, often within hours, and may lead to death.¹

First described in 1989, AEP usually occurs in previously healthy young adults who present with symptoms that have usually been present for less than 1 week and for which there was no discernible precipitating event.² Some cases, however, have followed environmental dust exposure or the initiation of cigarette smoking or have occurred as a noninfectious complication of AIDS.

Some patients have high fevers, pleuritic chest pain, and eosinophilic pleural effusions, the latter being a useful distinguishing feature in patients with diffuse infiltrates. All patients present with some degree of acute respiratory failure, and up to 50% require mechanical ventilation.

Since AEP is a one-time event and is very sensitive to treatment, full recovery can be expected. There is a report of one patient in whom AEP recurred after reinstitution of tetracycline therapy.^2,3 In several cases of AEP, cigarette smoking was the suspected cause, but no recurrence was recognized despite the resumption of smoking. It is, therefore, hypothesized that tolerance might develop in smoking-induced AEP.⁴

BAL should be performed early, preferably after tracheal intubation. The samples should be sent for identification of selected pathogens and a differential WBC count. In addition to excluding the occasional diffuse fulminant viral pneumonia or atypical pneumonia caused by Mycoplasma pneumoniae, Legionella pneumophila, or Chlamydia pneumoniae in the immunocompetent patient, the results of the differential WBC count may obviate the need for further intervention. BAL fluid eosinophilia in this setting establishes the diagnosis of AEP.^2,3

Corticosteroids are very effective in treating patients with AEP. The literature reports more than 50 successfully treated patients.² Complete resolution occurs within 7 days, without residual physiologic impairment. In the vast majority of patients, AEP does not recur.²

The outcome of this case

High-dose corticosteroid therapy was started, and the patient's condition improved significantly. He was extubated on day 4. On day 6, he left the hospital on a regimen of tapered-dose corticosteroids; his oxygen saturation was 97% on room air.

References:

REFERENCES

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2. Schwarz MI, Albert RK. "Imitators" of the ARDS: implications for diagnosis and treatment.

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3. Allen JN, Pacht ER, Gadek JE, Davis WB. Acute eosinophilic pneumonia as a reversible cause of noninfectious respiratory failure.

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4. Shintani H, Fujimura M, Ishiura Y, Noto M. A case of cigarette smoking-induced acute eosinophilic pneumonia showing tolerance.

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